Ask Charlie: Flying changes dressage vs jumping

Jill asks - "Why is it that training and executing flying changes seems to have an entirely different connotation in showjumping than in dressage?  My (limited) understanding is that flying changes in dressage are considered fairly high level, can be difficult to train and are only attempted on a horse that is well developed in all preceding movements; learning flys is like a dressage right of passage.  Yet  in (my very limited) observations of showjumping it seems that changes are introduced early in a horse's education and executed with very little fuss.  What's the distinction between the two disciplines? Or am I misreading the situation entirely?