The general idea of the universe in Alabaster, from the start, was to be entirely canon compliant to Homestuck BUT to develop the universe by adding a lot of things, expanding it rather than staying stagnant.
SGRUBrip tries to go from the usual mechanisms of SBURB/SGRUB and to add a multi-layered twist of a "broken" session. But generally speaking it follows the established rules.

(This approach made more sense in 2011 than it does in 2023; since, we've had the "Void Session" in canon and countless broken/pirated/glitched SBURB fan sessions.)

I did some limited mistakes on the way, the most significant one being, once again, the Prospitian clothes which follow the reversed Harlequin palette.
[ https://mspfa.com/?s=236&p=2432 ]
If I restarted Alabaster today, their clothes would likely be dark blue at the beginning (the reversed palette to the orange Decapitateball clothes) etc.
But this one error will stay since I like the results and it doesn't threaten continuity or the political/ethical implications or anything. I've also found a simple in-universe explanation.

Now to deal with the core of your question.

Alabaster Alternia follows the same general logic than the one applied to the more general Homestuck setting. The idea was to stay true to Homestuck Alternia but to expand it.

So I expanded on the musclebeasts and other xenobiological or cultural stuff...
[ https://mspfa.com/?s=236&p=69 ]
The sicklehead shark is an example of direct extrapolation. In canon, John has a hammer and Karkat has a sickle. We have hammerhead sharks on Earth. So...
[ https://mspfa.com/?s=236&p=51 ]
The main idea was to always make things as grotesque as possible, to take jokes and to turn them into serious and sinister elements. Alternia is clearly a nightmare world in more ways than one. It is horrific but it is also -surreal-. Hussie worked from bad puns and old scifi archetypes and took the idea further.
So I added more bad puns and archetypes and worked from there with a general hard science fiction approach, trying to reach consistency, to really see how the Alternian ecosystems and Alternian culture could work. That's the general move for all of Alabaster Alternia.

It ends up diverging in some ways from Homestuck Alternia as it was developed in late Acts of Homestuck as well as in the Hiveswap games.
I always tried to keep Alabaster Alternia architecture brutalist and a little ugly, for example, if not downright absurd and Timburtonian.
[ https://mspfa.com/?s=236&p=2547 ]
I like the ugly grey concrete.
Meanwhile, Homestuck Alternia evolved into a more colorful and futuristic interpretation. It went in a radically different direction, particularly with Hiveswap's very bright and psychedelic palettes.
So against my will, yeah, Alabaster Alternia became its own Alternia in some ways. Originally the aesthetics were built from what we see in Hivebent and nothing more.
It will keep this kind of palette and keep developing its own specificities in culture and ecosystems.
I don't think I will use the New Alternian Alphabet for example, or only for some tiny details.

This answer is drifting in a lot of different directions at once, and if developed further it could reach novella proportions, so... time to sum it up!

Bullet points:

• Yes, Alabaster Alternia has specificities, the culture and xenobiology were developed following hard scifi worldbuilding principles building from jokes and archetypes (basically the Hivebent approach but a little more in-depth).
• However, it was not part of the original intent, the differences with canon Homestuck Alternia originate in the fact Alabaster is an early work.
• It may make more sense to now occasionally call it "Alabaster Alternia".
• I will keep working the same way and not contradict what I developed before, so the differences with canon may continue to pile up a little in the future, even though to remain "as canon compliant as possible" is still in the goals.
• I now work with Cerulean Snake when it comes to worldbuilding; we've united our settings under the name C.H.A.O.S. (Cerulean-Homestuck-Alabaster-Oasis-Snake). C.H.A.O.S. is our free interpretation of the Homestuck setting.
• We do take Hiveswap into account occasionally, the complete Alternia map in the Ausira flashback was made by merging cartographical data of Homestuck and Hiveswap.
• Our general rule when it comes to the sequels and spin-offs is "We take what will fit".