i think he's changing for the sake of fan service and expectations rather than character development bc ppl want to see a weak more feminized seth get coddled and protected by big strong man horus. they're the endgame pairing so they're trying to facilitate the relationship quicker to deepen the relationship, but it doesn't feel organic to me.
og happy seth (before osiris blew everything up) had a distinct masculinity to him. vengeful seth had a range of exaggerated expressions that just made him feel so fun and fresh. repenting seth COULD be more vulnerable, but the way he's depicted now just seems out of character for me. someone as prideful as him needs at least a few more character arcs to to reach somewhere near this point, and i don't expect his features to get softer or rounder in the process.
i miss hotheaded gremlin seth from s1. he’s been gradually yassified more and more, in looks and personality