Height is linked to jumping - thus a 5'4'' tall player will never get a 20 jumping.
But it isn't a straight translation (ie. not all 20 jumping players will be 6'6'' tall).
Height is thus NOT used as a modifier for jumping, this is simply because doing that would reduce things to maths exercises in your head where the answer would be impossible to know (ie. exactly HOW many inches does jumping 20 mean someone can jump?