Reversed elevator effect?
I'm not a pilot but in my work I get in contact with different aspects of flying.
There are so many posts in this thread that I can't read them all. If what I'm going to suggest is mentioned in an earlier post I apologize.
Although I have never heard of it I wonder if in a stall situation like this there could be a phenomenon that could be characterized as a reversed elevator effect?
In this stall COP is obviously forward of COG and the horizontal tail must then produce a high lift (upwards) to rotate the nose downwards.
Hypothesis goes as follows. At this aoa plus the extra 13 degrees of the HT, the HT is probably stalled too. Pushing the sidestick forwards in order to gain more lift on the HT will move the trailing edge flap (elevator) of the HT downwards thereby giving the chord line of the HT a higher aoa resulting in deeper stall of the HT and less lift generated by it.
Pulling the sidestick backwards moves the trailing edge flap of HT upwards giving the chord line less aoa, a milder stall, more lift on the HT and a lower pitch angle.
If this hypothesis holds it could explain why the PF pulled on the sidestick