Originally Posted by
LHR/MEL/Europe FF
Doesn't matter. If the OP is using the lounge before entering HKG they are using it as an arrivals lounge, not a departures lounge.
if there were a rule stopping that either AA or CX would have pulled it.
add to that cx staff suggested that makes it unlikely that theres actually a rule against it.
more reason to think its a made up rule and lazy staff.