All new features are gated behind feature flags that progress from the developing team, to all GitHub employees, then to public over a multi-week span. Larger changes like this one have an internal discussion post shared with the company and a changelog entry once published.
I'm not sure that's all that much better. I'm not sure what's worse. There not being QA, or things just flowing right through QA. I guess still the former, since when there is QA, it's probably still filtering off some of the insanity. It's just that it's never seen by the greater public.
Big assumption you're making there.