I suspect it's because you need to do
from salted.__main__ import Salted as Salted
instead of
from salted.__main__ import Salted
Or typecheckers won't consider it a re-export.
https://www.python.org/dev/peps/pep-0484/#stub-files
I'm not 100% sure - since the pep only makes the claim about stub files. It's pretty easily reproable by setting up
from salted import Salted
And running mypy --strict testfile.py