Waiting to deplane a VA 737 today the aerobridge was connected and J class pax disembarked. FAs held Y pax onboard with the explanation that they were awaiting rear stairs to be connected. A row 3 pax (prob a WP) asked why. The answer was "weight and balance, we don't want the plane to tip over".
Really? I can imagine that situation might happen (maybe) in reverse by 180 pax pushing toward the tail might lift the nose, but how many times does a 737 only use the door 1 aerobridge without a problem.
In the end our rear stairs didn't arrive and we used the aerobridge anyway!