By the way, updating setuptools_scm to 7.0.5 did indeed fix the __version__ error.. Now setuptools_scm generates the proper variables in _version.py by itself.
Uch, go mod vendor does not fix the fact setuptools-golang itself calls go get -d from inside the compiling phase.. Seems to be a reason why there isn't a Gentoo ebuild for that setuptools extension 
Maybe I can just strip that out of setuptools-golang too 