I was just going to reply on this topic and here it has its own thread.
I'm actually more in agreement with @Derp than not. He's not letting friends play banned concepts. Something that's restricted is not banned. Staff still allows it, you just need to get their approval first. So what does staff use to determine whether someone is allowed to play a restricted concept? Their opinion.
Does it really matter if they only met this person on that game three months ago? The person has a limited track record on that game but they seem sane. Staffer instinct? Yes. Is that really better than if the staffer knew the other player for a year elsemu*? Or for two years doing tabletop? It all comes down to the same thing: they think the person won't abuse the concept and will benefit the game. Every player is judged on the same criteria and has the same opportunity to play that concept.
Now some caveats. Is there a quota? That gets a lot more grey. Do the rules specifically say the person must have been playing for X time first? That's a violation. I could go on but I think my point is clear: if you trust the staffer to decide who gets to play something, they should be allowed to use their discretion so long as everyone has the same opportunity and it violates no existing rule.
If you don't trust staff, don't play there if it bothers you that much. If you do play there anyway, suck it up. You made your choice.