Obviously source control has its benefits, but ironically often tarball-only developers produce very high quality software (the most prominent example is djb at cr.yp.to).
Conversely, GitHub is full of low quality software.
Conversely, GitHub is full of low quality software.
None of this is to claim that he's a bad cryptographer, or even a bad software engineer. But pure code output is far from the only important metric for software. GitHub makes it easy to do release engineering well, or to let other people help you with that if it's not your forte. (libsodium, for instance, is on GitHub.)
Now go on, make it another -10; it will be the only thing in your day that makes you feel that you have any influence.