I think the video above is more indicative of less than perfect technique than any susceptibility of the 777 to PIOs. I’ve flown it for some time and IMO it feels and responds like an aircraft with conventional controls, apart from not needing back elevator in turns and removing most of the effects of thrust and configuration changes on the trim.
It has very good aileron authority at approach speeds so if you give a disproportionate response to a roll input, you could end up over controlling. That applies to most aircraft, though.