Sciolistes
Somatographic illusion is only one possibility, not necessarily the answer, but it is a well known phenomenon and with the power pitch couple it may cause the crew to either push forward on the control column or trim nose down or both. I'm not sure why you feel it is unlikely.
The subsequent low nose attitude and presumed high power setting would cause the aircraft to accelerate very rapidly giving the illusion of a pitch up, If the crew pulled the power back, this would make the aircraft pitch down even harder and given the extreme low nose attitude, the PFD would not look familiar to the crew and the pitch attitude would look unusual, the crew may therefore have relied on seat of the pants instinct and reacted to what they felt instead of using the information presented.
Flight simulators cannot replicate the somatographic effect, but instead, they rely on tilt angles to fool occupants into thinking they are manoeuvring such as accelerating down a runway while remaining firmly bolted to the floor.
There is no doubt that the aircraft was accelerating, very rapidly, toward the ground, as confirmed by the videos and the above mentioned fs24 data, laws of physics again.
I would tend to prefer the known science and lessons learned from the past and am not swayed by the unregulated data supplied by fs24 which seems just to confirm the obvious, eg, the aircraft started to climb, then descended rapidly.