It's a very small lounge so I suspect they are playing the capacity card based on pax they expect to arrive. There are a few in the network that do this, but its certainly the exception rather than rule.

CX807 leaves at about the same times as the AB flight, and BA294 only a couple of hours later.

Have seemingly done it before with CX pax
http://onemileatatime.boardingarea.c...unge-is-empty/
http://onemileatatime.boardingarea.c...icago-airport/