Five hundred feet for scattering of aircraft debris (even large parts) is not very far when you consider a hard, uncontrolled impact in the case of spatial disorientation. Water can easily move/shift debris fields. We also have to take into consideration the first-moment scattering of aircraft parts that resulted from the actual, initial impact. Rescue personnel and investigators did not reach the scene until more than 12 hours after the accident. Things move. For all we know the aircraft hit the water and cartwheeled a distance as it broke apart.
I flew that night. It was a moonless night and hard core IMC. (July 2 was the new moon/no moon and this was just the night following). A perfect recipe for disorientation and and an uncontrolled crash into the water.