Maybe it was part of his natural broadslide.
If you watch old footage of Penhall I have noticed that compared to most other riders he almost over steers with his back wheel coming out of bends. Whether there was a rider near him or not he had an uncanny habit of doing this. It is clearly evident in the '81 final where he was constantly trying to make long straights.
I have watched many Penhall races on video and to me this was just part of his style.
Me personally. Still can't make my mind up if Carter was pushed or simply fell.
One thing is for certain, he had "Noooooooooooo Chance!"