Legendaries could be better, but I'll take them, definitely much better than the latest pair.
I'm guessing sneaking behind a Pokémon simply gives you an advantage, but it doesn't seem like there's more to that and it also seems like you can't move around during battles, I liked that a lot in Arceus, that and the character taking a serious stance when commanding a move.
Couldn't care less about co-op tbh, hopefully the game is not mainly designed with that in mind.
Also, weird to have Japanese-based names for the Legendaries in a Spain-focused region. Maybe there'll be lore reasons for that.