They announced this exclusively on X.com, which ranks barely above Pinterest in terms of usage. That's below Reddit, Snapchat, WeChat, and Instagram, and requires a user account to view profiles and posts. And that's ignoring all the reasons X is a divisive platform with an extreme political bent.
GitHub chose not to announce this on any other social media either (BlueSky, Facebook, TikTok, YouTube, LinkedIn, or Mastodon, as of this posting, and with no emails sent on the matter.)