I'm interested to see what Brian has to say concerning video.
Most of the AI's, I'm fairly certain, use video to check plane. I know of one , that will not teach without video.(except for some short game instruction)
It's cause from DLT.......the hands and club essentially move off a vertical plane thru the hands at Address (i.e. if you draw a vertical line through the hands at Address).....so you can only really get two "pure" views of the swing....
i.e. if you centre the hands with the target when the golfer is at ADDRESS...
The only time it will be right is at Address and then again at Impact...
The rest of the time it will look laid off (not sure to what degree).