I was told by a friend that reversal of control occurs on the backside of the power curve.
Maybe he referred to "stumbling over one's ailerons" as Langewiesche puts it. When mushing along in extremely slow flight very close to a stall a downward deflection of the aileron might not lift the wing upwards as it would in normal flight but (aside from adding drag) increase the angle of attack beyond the critical threshold, making the wing stall and drop instead of lift.
Example: stick/yoke to the right means left aileron down, right aileron up. In normal flight this pushes the left wing up and the right wing down, banking the aeroplane to the right (which is what you want). The same thing very close to stalling angle of attack could make the left wing stall and drop (because of the downward movement of the left aileron, increasing the angle of attack of that wing), making the aeroplane bank very sharply and suddenly to the
left.