I don't think marcan is making the argument that you can't comply with a link to github, that's very much the canonical way to do it.
It's just very easy to mess up if you do it this way. Like, let's say that you make your software link to its source on Git. But then you also package it as a .deb / .rpm or whatever, and during this packaging process you apply a patch. Oops, suddenly you're not actually linking to the source code of your modified version anymore, not compliant.