Should just cause a DF strike if you get kicked from duty, same thing that stacks up if you withdraw from a DF queue pop, since it's the same effect whether it's a real 90k or fake - you're wasting the time of the pugs in queue.

If it's a real 90k or a real situation to withdraw, then it's not a huge penalty unless you've been constantly 90king/withdrawing all day - at which point you should fix your internet or whatever situation caused you to constantly withdraw from queue instead of continuing to queue. If you constantly get kicked from duties you should probably reflect on yourself why it's happening.

If it's a serial faker then they'd have requeue penalties until the next day so whatever.