Hi lovely! You are correct I have mentioned a headcanon gmg timeline but I actually never fully wrote it out or posted it anywhere, so please don't apologise because you are 1000% correct <3
I'll give a summary and I will be referring to Berry's timeline for reference (if you haven't read it, please do, it's an important piece of literature): https://twitter.com/mon5nge/status/1830020411829977267

Pre-Debut
I think everything was hectic. Chaos galore. Queue the gif of Troy from Community holding the pizza box in a room set on fire. I don't think they even had time to feel things much other than try to get to know each other. So that was very much casual friends learning to friend some more and get closer.

Debut
I think there is a general consensus that Geon started his crushing kind of early on from debut. It was kinda cutesy crushing, casual, I think Maet very much is his type but he treated it superficially and wasn't sure where it was going to go so he kind of was low-key about it? Partially because Geon I think tries to act low-key about a lot of things that actually mean a lot to him. He's a giant nerd with a big heart but he doesn't want to seem uncool so he tends to play things more coolly than what he feels inside.

I think during that time, Maet was also getting closer to Geon and saw him as a sweet dongsaeng. I think they both realised they were compatible, but I don't think Maet was considering anything romantically at that point? His head just wasn't there but I think both were really enjoying getting to know each other.

Between In Bloom and Crush
THE BEGINNING OF TENSION! The high from debut was settling, they're starting to get into a little bit of a rhythm, be more familiar with how they (zb1) as a group socialise, how to navigate around one another. I think this small lull created an opportunity for them to get closer and maybe start flirting a little? Maet is flirty by nature and to be honest Geon is too. I think they both maybe started experimenting with their flirting and touching a bit more. Still platonic, not an obvious blurring of lines in any way - but a gentle poke at the line. Occasionally stepping over it and saying something that could be construed as romantic, but with the excuse of "oh I'm just kidding!" as an excuse to hide behind. I think their late night conversations got longer, their cuddles became a daily routine and they really started to look at each other and think, "could I rely on this person?"

Crush Era
Chef's Kiss, a name synonymous with what was going on with gmg at the time. I think Geon's crush was pretty solid at this point, he knew he had a crush on Maet and was just waiting patiently to see what would happen with it. Geon isn't the type (imo) to take the lead if he doesn't know what the ending destination will be, and I think that he really wasn't sure of Maet's intentions either. I mean we all saw the Idol Radio clip where Geon's face was BRIGHT RED - poor baby was caught off guard when he got given that rose, he was flustered. Whereas Maet was beginning to acknowledge Geon's crush and play with him a bit because of it, I think he wanted to see what Geon would and wouldn't be agreeable to. I think the way Maet and Geon view romance and relationships somewhat differently, so Maet's version of an action with a romantic intention behind it is a bit more obvious than Geon's. Not to go back to Maet's astrology chart (again) but he is someone who accidentally is prone to leading people on due to his natural flirtiness and has and will continue to cause him problems. So I think Maet probably used his natural flirtiness as a disguise to hide behind. He was wilding quite a lot in this era and got shipped with a lot of different people for a reason. So I think he probably used that as an emotional shield for himself and saw it as fun flirting. But I also think it was during this time that he really noticed Geon's crush on him, so he started stewing on it a bit, considering what it meant.

December-February 2024
Geon turned 19! And I think that changed a few things for them. I think Geon got a bit more confident with his new status as an adult, and I think both of them got a bit more truthful about what they meant to each other. I see gmg as a romance built on friendship and trust, they liked each other as people and as friends and co-workers first before anything else. At this point I think they really trusted each other as friends (talking about their insecurities, struggles etc.) and that this translated to them bonding deeper on an emotional level. And this is where the REAL blurriness between the lines of friendship and romance began for them. I think the Japan-trip in particular is a massive indicator of that. They weren't all over each other or anything, but it really confirmed to both of them that they enjoy spending time together, even when they're not working. Their friendship had blossomed to a point that they had become one another's pillars (which is around the time I joined the fandom), so then it became a question of... what next? There's only so far certain actions can be deemed acceptable in friendship, and they were hurtling towards something unlabelled but beyond the bounds of platonic friendship. Their actions got flirtier, their looks got more heated. The crush was mutual and the game of gay chicken they'd been playing no longer felt quite so... harmless.

And that's when I think something happened. Considering how cautious Geon is as a person, it was more of a talking things out than a taking off each other's clothes if you know what I'm talking about. I think they may have kissed, acknowledged that what was going on between them wasn't entirely platonic, and agreed to see where things would head for them.

Yura Yura Era
It was like something had been settled between them. A sense of calm that meant we suddenly saw looks starting to be shared between them that can only be described as 'intimate', the whispering, the leaning into one another. I think this is where we see more of Geon's 'vulnerable' side being revelaed to Maet (as well as all of zb1, but especially Maet), where he started to allow himself more quiet moments, more alone time where he wanted to just be quiet and not idol Geon for a moment. We start to get sightings of them going out places together, we start to see small actions where Maet treats Geon differently to the other members, really subtle things that have interesting implications. At this point you could tell Geon was on Maet's mind a lot because he ended up giving a lot of answers related to Geon, and we even started to see a bit of jealousy on his side too! I mentioned in a previous ask, but for Maet, jealousy is a good thing for him. It actually makes him feel more secure in his feelings rather than insecure because it reaffirms that he does have feelings for this person, he's not stringing them along.

Feel The Pop
Ok this is when they fucked. LMAO. And when my infamous tweet became infamous. We started to see some very cute possessiveness from both of them in different ways, they both expressed how they liked to spend their alone time together (which is still crazy to me, some of the most romantic shit they've said fr), Geon cheesing as he proudly mentioned Maet in his lives, Maet talking about how he ONLY kissed Geon? They were going crazy with their flirting. The push and pull. The 'playing hard to get'. Geon wanted to be chased and BOY did Maet take up the challenge! The tension between them was insane. They couldn't keep their eyes off each other, their hands off each other, talking about each other constantly, the members being sick of their shit... and then suddenly it was ok? That in my opinion suggests a massive amount of tension that finally burst due to release. So yeah, I think around April-May they fucked for the first time and decided they were serious. I think they'd been building up to it, exploring things together, seeing if it was just puppy love and kind of giving each other time to adjust to the idea of dating. And then I think Maet probably did or said something that Geon had been waiting for and they were like damn! Okay! We're doing this I guess!

So I think they had a few weeks after they fucked where they acted crazy obnoxious which pissed off the other members (around the time Maet complained about the 1:1 date and the fan-kit shoot). Cause bro people do not appreciate how crazy Maet touching Geon's ankle was and looking at him like that... that's just. To me that is truly what sealed the deal. That was such a subtle boyfriend behaviour. And yeah so they were living off that high for a while and things calmed down a bit after. It's hilarious to me bc the peak of them wanting to rip each other's clothes off all the time was at the height of the FTP promotions (spotify, heart rate, fan kit, fansigns) so June was just... yeah they had a great time in June. Congrats and I hope all the effort in the gym paid off for both of their stamina!

Good So Bad
And now we come to current time! They're still crazy, telling us all the adorable tidbits about their relationship, still very gay, and probably in love too. We see them going on their dates, talking about each other happily and kissing each other on camera? Like ok boyfriends. This era isn't that different to FTP and it's much shorter but we're starting to see a more serious acknowledgement from the other members that these two aren't just fooling around, that they're serious about each other. And I'm very happy for them! Long may GMG live!!

Thank you for this lovely ask anon 💕