dh, agree.
SI involves acceleration; generally longitudinal, and lesser in non-turning flight while pitching up. A GA contributes little speed change nor great rotation acceleration, usually very short duration and thus insufficient for disorientation.
This appears to to be the reasoning behind the conclusion in the accident investigation.
The pitch - body feel - stick / trim feel aspects could create a different illusion.
I recall that there was a very interesting 757 event during GA where this could have contributed.