Maybe he is not that gregarious? Not every hobby needs to be social activity.
It's such a low-stakes hobby, and I don't need to care about collaboration or "efficient progress." The local HAM radio group is a bunch of elderly guys who just talk about Trump and their sore backs, not my cup of tea. For some things, you can have plenty of fun alone in your computer room.
(Of course, when we use technology and read books, there is a remote participation in the social as these are cultural and thus social products, but that's not what is meant here.)
He posted it on Reddit. That's pretty much the definition of both gregariousness and social activity.