The GetInstanceRemovedSignal still fires if the part is parented to nil but not explicitly :Destroyed.
As for my usecase… well I can’t remember exactly why, to be honest. It’s been a year since I posted the OP, after all. But there are several threads out there (this and to some extent this) which show some reasons why one would want to check if something was destroyed.
EDIT: Meant to reply to @Kampfkarren