Sure, but it's not just the reoo. It's PR's, code review and you've got a bunch of actions then it's difficult (not impossible) to deal with those being down.
Don’t let yourself get so locked in ideally, but still keeping the code online is still quite valuable to a lot of folks.
Sure, but you have to remember that a lot of companies use the issues/trackers/PR heavily as part of their development flow. If they go down, new work can't be scheduled.
Downstream often still relies on fetching & doesn’t care about any of the clerical stuff. Folks should consider self-hosting that clerical stuff anyhow given the independence you get & given MS GitHub’s uptime over the last several years.