[r-s]

There is no reason someone couldn't change commit dates and be prolific far earlier than December

[thih9]

Lack of pre-december github activity could be an indicator, i.e. no pull requests, no issues, no stars or forks, perhaps even no feed updates, etc.

[pnt12]

Lack of github activity may also be an indicator for having a life outside programming. Or using private repos.

[zimmund]

Or just being as prolific on Gitlab, Bitbucket or elsewhere. We have to stop taking Github contributions so seriously.