> What many fail to understand is that disinterest in Github absolutely does not tell you anything meaningful about that programmer.

Well, it does. It says he doesn't have a portfolio for some reason. Is it because he is incompetent and has nothing to show for? Perhaps not, but if the candidate makes it difficult for recruiters and interviewers to get an objective way to corroborate his claims regarding his level of expertise then just for the sake of avoiding wasting your time with yet another paper tiger... It would be better to cut him out of the shortlist for further interviews.