Having __del__ present in stubs is useful for a few reasons:

• A subclass that calls super().__del__() would see a false positive if __del__ is present in the base class at runtime but not in the stub
• The documentation explicitly states that subclasses should call super().__del__() if they override a __del__ method. A type checker that wants to enforce this rule would need to know whether __del__ exists in the base class.

See discussion in python/typeshed#10984.