It's more of a "this was deleted, we suggest you do it too". Ultimately it's open source so anyone can modify this stuff to their liking and individual instances can choose to go along with a delete suggestion or not.
You should theoretically also be able to tag something as deleted but only actually delete it after a week (for example). This would comply with regular delete suggestions and keep things synchronized as one would expect but would give a bit of time to defend against an instance going rogue and self destructing.