Note that GitHub's "source code" automatic downloads are not release tarballs
At first I thought you were talking about the "Clone or Download" button that lets you download the repo in a zip file, which seems obvious that it's not a "release tarball", but upon closer inspection, if you click "Releases" tab along the top and then grab the actual tarball presented for the release, it appears to just be a tarball of the VCS source, without the `configure` script and `Makefile`s and such already generated. I could see this being confusing.
I wonder if there's a way to get Github Releases page to link to the actual release tarball instead of the non-release tarball confusingly linked there?