I disagree. PyPI is basically a packaging environment, so using the tarballs from there would mean we are then subject to the curation decisions by the people who package the PyPI releases before we even get the sources for the package (which may or may not be the upstream developers). Additionally, using the GitHub repo as the source of the package would seem to fit the spirit behind the packaging guidelines more (
https://docs.fedoraproject.org/en-US/packaging-guidelines/SourceURL/) - where it says "For the Fedora packager, this means that sources used to build a package should be the vanilla sources available from upstream."