Well... "Respawning" does have some lore to go with it.

Notably inferred lore. Specifically in the HW BLM quests. Wherein you get yelled at for "Not being able to control your power" because you apparently KILLED the cultists that were attacking your friends. (Though, it turned out that their deaths were not your fault and instead due to them using Black Magic without a Soul Crystal causing them to set their souls on fire due to the sheer power they're attempting to wield)

Which implies that typically, you DON'T kill enemies, even though gameplay wise you bring them down to 0 HP and then watch them fall down.

This also is referenced in other quests too where you will fight someone and essentially "Kill" them gameplay wise (I.e. Bring them down to 0 HP) yet they're still fine and continue to exist in cutscenes post-fight.

So, there's likely some sort of gameplay mechanic > lore happening where we bring enemies down to 0 HP just because it's more obvious that they're finished with than if they drop down to their knees and stay there in the fight (Like happens on some occasions), while in actuality we don't kill all of the enemies we beat, likely only actually killing beasts/monsters while just pummelling people into submission.