This is not even speculation, just a "scenario" that might fit that reported throttle and control-input reading.
Massive incapacitation of PF (bird through the windscreen, medical, other), body pitches forward onto both column and (hand) throttle levers. Nose-over forces make it impossible for the other pilot and jumpseater to clear the controls until too late (that possible last-second attempt to get the nose up).
EDIT: I see I'm not alone - but it would certainly require a "Black Swan" event.