I didn't get EUA'ed for my MSP-LGA flight sunday night (last one of the night, on a 755)--no surprise since I'm currently silver and the premium section of Y had looked awfully full when I last checked on Friday.

I asked at the gate whether F was checked in full (just in case), and the GA pulled out a stack of at least 5 or 6 battlefield BPs to look for my name. Most were plats, with just a couple golds. So I'd agree that they're probably holding more F seats for walkups on certain flights.