BOAC:
- I would question that definition. A 'PIO' is any oscillatory instability INDUCED by pilot input, most commonly caused by pilot input applied to dampen a disturbance is applied incorrectly so as to be 'in phase' with the disturbance, thus either worsening or at best maintaining the oscillation. What you describe would be a particular form of 'PIO', not within the general definition.
Another term I've heard used is "Pilot-in-loop" oscillation. It's a servomechanism or control loop in which the pilot is part of the loop. It's difficult to assess or predict when/where this can occur, because the mass and dynamic response of each pilot's arms and legs is different.
And it doesn't matter if the initiating input is voluntary, or turbulence, or whatever. If it's an unstable loop, the oscillation will grow in amplitude.
The correct action is to LET GO of the controls, to break the loop so the oscillation can stop, then drive on.