Airbus write a procedure that covers every fuel state from all tanks full to minimum landing fuel, and it is left to the crew to manage the fuel system safely. There may be trim tank fuel, or centre tank fuel if fitted. MONITOR FUEL IMBALANCE covers every situation.
The a/c location is also relevant - at FL 350 over Europe, if you land asap at an aiport 100 miles away, what will the fuel imbalance be if you leave the crossfeed shut? 1,000 kg?
But if you are EROPS the maximum allowable distance from an alternate, you will need to manage the fuel balance.
It is easy for a TRE to fall into the trap of thinking in terms of simulator training/testing only - which may have happened in this case...