I see what you all mean. I am in no way a jumper. I have never been with an actual trainer, but my parents took the advice of the more experienced people around and by the time I was 6 or 7 I was walking and trotting on teh lunge line. I think that in any discipline it is important to master the basics before moving on. Too many times you see people trail riding, jumping, doing poles/barrles that have never actually worked on their balance. They sit on the horse, pull on its mouth, and attempt to catch themselves if tehy start to fall.
I do understand putting someone on the small poles or jumps to train the canter. I was lucky enough to learn while I was a little girl and thought I was invincible. I think there are very few exeptions though when theat should be done. In general a person should be able to w/t/c in acontrolled manner before doing anything more advanced.