I was an interested "bystander/bysitter" ....but not for long
Wiggy, your description of that PIO incident is fairly typical. It usually takes a second person freezing the yoke to stop a PIO because the the flying pilot is too immersed in the problem to realize what is going on.
Afterwards, your PF was probably very confused about what had just happened, right?
How big were the roll oscillations?
About all a PNF on an A type aircraft can do is take control. PF will probably be so highly stressed that his/her ears may not work.
FWIW, you are only the third person I've encountered who has seen a PIO up close and personal. Thank you for taking the time to respond.