That's explicitly called out by miedzinski, the PR author, in the discussion [1]--although for some reason it's mentioned as PEP 512 but links to the same page

That's explicitly called out by miedzinski, the PR author, in the discussion [1]--although for some reason it's mentioned as PEP 512 but links to the same page you mentioned. [1] https://github.com/python/mypy/pull/2761 https://github.com/python/mypy/pull/2761