So, don't accept an offer at Facebook unless you're confident you'll shine in the first months (even in unfair situations, with people working against you). I can see how it's great for the morale of those who pass the hazing, but it sounds like perhaps they need to work on their on-boarding process - that incumbent teams and engineers are guided by selfish incentives that have nothing to do with helping newbies succeed.

On the other hand, those rejected will always have hurt feelings, and at some point their failure will be sealed by the lack of confidence/patience/charity established engineers have for them.

Probably the incumbents are often failing to appreciate the body of domain (FB procedures + code) knowledge they've accumulated, and that a new initiate likely lacks. Engineers are often poor communicators in that sense.