(Not at extramileage specifically) - why do people feel this is a problem, if they need to wait for a while to find out? I've had the opposite experience where (in DXB) passengers have definitely moved from a full J cabin to an F seat, to allow me to upgrade. This was on flights where Y was not oversold.
I was really pleased with this. You should try flying an airline like BA, where such space-available upgrades don't exist.
well if you want to use the F lounge in DXB it would be annoying to wait until the gate....