After touchdown, but it rolled sideways not end over end. This kept the fuselage intact and ripped off the wings (where all the fuel is) which is why everyone survived.
In larger aircraft that do have the ability to dump fuel, the reason is to make the airplane lighter so it does not have do an overweight landing and the subsequent high-cost overweight landing inspection. It is not done to reduce the probability of a post-crash fire.
I think parent was saying the roll was along the planes' length rather than tail-over-nose, the latter usually result in the aircraft breaking up as the torque will be really high.
- longitudinal axis: roll, controlled by ailerons.
- vertical axis: yaw, controlled by rudder.
- lateral axis (through the wings): pitch, controlled by elevators.