Whether the belt rubs or slips, you are in trouble, as its going to burn out and break. So I very much doubt VW spent money on a stop that isn't necessary.
Derailleurs on bicycles have no stop on them to stop the bottom jockey wheel rubbing the cassette if the chain is allowed to stretch too much. Again, only a situation that can arise due to a serious lack of maintenance.
I, and everyone else on this thread still don't understand why you are asking a hypothetical question for a situation that shouldn't even come close to an issue.