There are different A330 weights. The latest ones to come out of the factory are now 242T, Cathay's most capable are 235T. That is an hour's worth of fuel difference.

​​CX also doesn't have centre tanks on their A333's which mean at maximum tank capacity + payload to bring it up to MTOW the aircraft would have an endurance to flame out of around 13 hours. Payload would likely need to be reduced to just above pax only to achieve that range at the 233 MTOW most of the fleet has, even the 235s.