Doesn't look like any "dangerous stunt" going on.
Apparently, the P-63 has notoriously bad visibility. Some are opining that the pilot of the P-63 simply may not have seen the B-17, despite the size of the latter...
I wouldn't call it "stunt" flying, but if you look at the video, there were a lot of aircraft in a relatively small area at low altitudes.
I would say that in itself created a more dangerous situation than otherwise would have existed if the aircraft were more spread apart and at higher altitudes.
These airshows are spectator events designed to entertain the crowds and the low altitude flying is what creates the "wow" factor.
The lives of these people and the irreplaceable vintage WWII era aircraft they were in, were sacrificed for the sake of entertainment.
That makes it kind of sadder still.