It's quite likely that Peterson was experiencing a somatogravic illusion, where acceleration, in the absence of visual information may be interpreted as a pitch change, leading to a control input opposite to that required. in this case, a slight descent and subsequent acceleration may have made him think the aircraft was pitching up. leading to a further nose down control input. It was not widely understood at the time and the report wouldn't have made reference to it.
This illusion was the subject of my MSc thesis. My cohort of students used to set each other challenges, usually making reference to something our supervising tutors would not realise. Our task for our MSC thesis was to include the name of a dead rock star. With this accident, I achieved three.