As I'm sure you know, we are not the only service with several ways to lose your flight contract before, during, or after OCS. I wonder what really happened to the guy you met. FAC is a B-billet, not a primary MOS. So you can do it for a while but it's not a permanent job you can have as a Marine officer. Also, typically, if you get DQd from flying, you aren't offered "Take this MOS or get out." You're either so screwed you that you get out, like one of my TBS buddies was medically retired at the ripe old age of 23, or you request (AKA get assigned) an MOS like everybody else.

I'm not trying to call you out, but for people who don't know, there's more to it than what the guy made it out to sound like. Too much stuff we don't know...was he booted during OCS? During TBS? Medical? Otherwise? Was he in flight school when it happened? All of those play a factor in how somebody is reassigned after being removed from flight training.