Yes, but Github is not just about Git hosting, it's about all those awesome social tools. If you use Issues as the main bug tracker, for example, you've got a problem.
So even if bugs.kde.org were to go down, we'd still be able to fix code at git.kde.org, and use the lists.kde.org mailing list archives to lookup bug details as a backup. We'd probably use a mailing list system that doesn't suck like kde.markmail.org or GMANE for that last part, but that's just shaving the yak...