Last week, I checked-in 531 at HKG (a dayreturn) and had requested to WL for 451 1 week before the flight. But the WL wasn't cleared until I asking for it once again at TPE lounge. The 3 CX TPE flights in that evening were oversold in both Y and J and only 4 seats were occupied in F when I checked EF at the night before. The F cabin was full finally and I was the only DM on UD according to the SP on UD. After this incidence, I do think BN is also a factor to determine opups.