Counterpoint: he's insane. He clearly does think there's this special, innate bond that being human gives them, and to a degree he's right-- they're both displaced in the Isles (at least at first) and have to fight for every inch of progress they've made integrating themselves into this society. When the narratives be foiling (why is my microwave now on fire).

Luz can see it, too -- hence why in s3 she was torn up over the supposed similarities in her and Belos's motivations, despite telling him that she's not like him in King's Tide. Ironically, in her Titan form she was closer to him than ever, both changed physically by Titan magic. I noticed on my rewatch of KT last night that Belos's wrist-tats glow when he starts the petrification spell, so I have to wonder if it that was his attempt at controlling the curse and channeling the magic that consuming Palismen had given him (as he identifies them as the source of at least his shapeshifting in HM). What I'm getting at here is Bro Probably Cursed Himself, in a dark mirror to how Luz was told by the Titan that she had to choose herself in the In-Between.