I have heard that by following Onspeed AOA technique (constant AOA /Speed) on approach to landing, one gets protection to a large extent from PIO events during landing.
In my opinion, these two are probably only related by the fact that a well flown approach has a better change of resulting in a non diverging flare and landing. (Simply; good approaches result in good landings).
The PIO which might result after flare will more be a product of the changing attitude of the aircraft as it comes into ground effect, or surface contact, not being managed by the pilot. The approach can be very stable, yet the pilot lets it get away from him in the very final moments.
The natural frequency of the aircraft in pitch will allow it to change pitch attitude rhythmically at a rate very close to the pilot's ability to react to that, and the pilot may apply control inputs to arrest the pitching at the exact wrong times, and make it worse. This is extra prevalent with flying boats, as the variable interaction of contact with the water vs the C of G, and center of lift fight each other. It is a vital part of flying boat pilot training to assure that pilots can prevent and get themselves out of this condition.
On the other hand, a constant approach on AoA is flown for a glassy water landing, or landing on a snow covered surface, where the altitude above the landing surface cannot be determined with precision. In this case, the approach is precisely flown on a fixed AoA, and descent rate to the point of surface contact. You could still get a PIO after that in some cases, if pitch control is not positively assured. It's different factors, not related to the approach at that point.
Does that help?