This is more of a curiosity question - on my upcoming flight, 3 days in advance I was on the upgrade list at #3 - and while the list at the top said 44 seats, 41 booked, if you looked at the seating chart there were 6+ seats available. (I'm 1k, and upgraded with PP to Polaris)
24 hours in advance, I was upgraded, and removed from the upgrade list, rather than appearing with a check next to my name.
Any rhyme or reason for that?