Yes, I completely agree with your reasons, and I figured you would probably have thought of this. I was just wondering if you should mention these reasons in the PEP under “rejected alternatives”? In a few years, this extension may be posted on python-ideas, and then it might be useful for that poster to see your rejection reasoning.
That said, @typing.override could support both usage with and without the base class. But I agree that use of the base class would happen extremely rarely (only in a very complicated inheritance hierarchy). But anyway, the use of a base class could always be added later if someone makes a compelling case for it.
If the consensus is not to include that functionality, we could add it under the considered ideas.
Fair enough 