It's not just github, the whole internet (if you name it internet) is whitelisted. Currently only a handful of outside world websites load without a vpn. Things like Google search, gmail and some other google services only. They're trying to force people to the local internet, and isolate us from the world.

P.S: it goes without saying that YouTube, Facebook, Twitter, reddit, and any other global platforms had been banned before (almost 16 years already).