In typeshed we've replaced all instances of : Incomplete | None = None in argument annotations with just =None (python/typeshed#14029). We've also added a check to flake8-pyi to avoid regressions (PyCQA/flake8-pyi#509). The reason for this change was originally outlines by @Avasam:

This is still interpreted as Any | None by mypy. And now more correctly interpreted as Unknown | None by pyright.

It would be great if we could change the output of stubgen accordingly.