Rules question on abilities copying removed permanents.

So I think everyone is aware of how removing a scute swarm in response to the copy trigger going on the stack doesn't stop a new scute swarm token from appearing.

So why is it that removing my creature in response to the [[orvar, the all-form]] trigger does stop the copy ability too?

the scryfall rules notes section for orvar has this impressive piece of word-salad:

"As the first triggered ability tries to resolve, the spell that caused it to trigger and that spell’s targets are checked again. Ignore any target of the spell that has left the battlefield by that point. If all of the permanents you controlled that were targets have left the battlefield by that point, the triggered ability will do nothing and no token will be created. If at least one permanent you control that’s a target is still on the battlefield, the triggered ability will resolve, even if that permanent is now an illegal target for the spell. (2021-02-05)"

but that doesn't explain why it works differently, shouldn't scute swarm also check again and fizzle when it finds the permanent it needs to copy no longer exists?