This kind of explains what happened to me last week. Y0 for my flight as well as the 1 before mine and for 1 after. F0 as well. Checkin at the AC and they tell me I am #3 on the upgrade list and 3 open seats. Just for kicks I call EXP desk and ask if I can buy a F ticket and they say no seats available. I check the seat map on EF and see 3 open seats. Did not end up on the flight because of a delay I would have missed a connection.