Hi Ian W
However, into this action PF was putting in as much aileron as he could, often apparently full SS. The result of this would be to make the low wing AOA higher so less lift so a tendency for the aircraft to apparently do the opposite of what was wanted until the wing sweep effect was larger than the aileron AOA effect.
I don't know the physics of stalled aircraft behaviour, but I think the stability was a result of dihedral rather than sweep.
When stalled, if one wing is lower, it presents a greater plan surface area to the airflow than the higher wing, resulting in a levelling couple.
I think PF's roll input would help level the wings because the lowered aileron would present more drag. (edit in the same way that down elevator lowered the nose and reactivated the stall warning)
However, I will probably agree with Owain's analysis.