JB thank you . Can the same issue happen with the same plane type but different configurations . I am thinking of the a330 200 with Qantas and how they have an international, domestic and a hybrid seating arrangement.
You'd never say that something isn't possible, because people are amazingly adept at finding new ways to make errors, but I don't think you'd be able to get enough of an error in different configurations of the same type.
Cargo...now that's a whole different ball game.
Once the problem was identified should the pilots have moved a dozen pax to the rear and would that have been safer for the low speed approach for landing.
They never really worked out that that CofG was incorrect. They correctly deduced that the trim setting was wrong, but not that the overall balance was badly out. If they'd done that, they could have contacted the company and had them run the loadsheet again, to get the correct figures, or, they could have done it themselves. I don't know if they had the ability to electronically run the loadsheet, but even a rough manual one wouldn't have taken more than 10 minutes (assuming they actually knew how to do it).
You'd probably need to move many more than a dozen. Alternatively, you could fill all of the seats around the centre of the aircraft, with nobody at either extremity. It's a dangerous game to play without any numbers. They found how easy it was to end up too far forward. They would not recover from too far aft.