I read the linked article the first time it was posted. My question was probably unclear, so let me try again: what happens in a crash that would prevent the belt release mechanism from working? It seems that unless the lock was damaged, it should still work.
Bigley:
My thought on this is that after a plane crash most people are disoriented, panicked. this level of chaos and stress can make a person try a seat belt (remember it isn't like a car seat belt) and when it doesn't instantly release or has some resistance they panic and think that it won't open.
Secondly keep in mind that "Seat belt maintenance" isn't normally a high priority, I mean when was the last time you brought your car in and told them to service the seat belts? It is possible that the force of the impact can notch the retaining metal and thus make it, "locked up."
Weather by rescue hook, box cutter, or opening the seat belt, I don't thing that the method matters, just that the people are OUT of there seats and are in a safe location. It would be my hope that no-one would try to salvage the seat belts from an accident like that.
Just my thoughts.