As a deterrent for abuse, it makes sense to suspend lots of accounts up front, pending investigation, and then let them back selectively as they are reviewed slowly. But if you're not doing the review, it makes no sense to ban lots of users while not addressing the root cause. That's just a way to run out of users.

I don't think that github is at risk of "running out of users". If the cost of doing the review is greater than the cost of losing those wrongly banned users, it makes literally zero sense to do the review