I don't know that I really believe that... 3 days before my prior flight (I can't remember what the seat chart said), but the booked/free - was the same - 44 seats, 41 booked, and yet, somehow - there were 6 (7?) people upgraded (who all showed up with checks/seat assignments) (no problem, I was #9 on the list that day). I'm just wondering why sometimes cleared upgrades show up with a checkmark/seat assignment on the upgrade list, or they just disappear from the list altogether (from my personal perspective, I don't care especially if I got the upgrade! More curiosity as to how the upgrade list works / especially how it shows up in the last few days before flight)