This idea runs in both directions, so to speak.
Each Form builds on the preceding one, however knowledge gained in a new area can then be applied to concepts that have been learned in an earlier Form.
Learning can have a generalized effect on related skills.
I can, with my limited experience, confirm this, as I found myself recently (in a video I've posted elsewhere on the forum) doing moves from Djem So in a form that was intended to be Shii-Cho based. Arguably they are the same moves (or very similar) and it is the application and concept that is different, but regardless of that, the high numbered forms enlarge your palette of usable techniques for the lower numbered forms.
