PIO
I agree that the roll oscillation was a PIO.
I'm not so convinced that there is a big difference between alt 1a and 1b, though there certainly is some.
In alt 1a the airplane would have been inherently more roll stable and probably would not have required much correction to begin with but given a 3/4 stick input in reaction to an 8° bank angle (exccessive), a PIO is still possible