That's a superb question! And I have an opinion, if not an answer.
I saw a tape of some QuickStep experts breaking down their routine into stuff that lesser mortals could do, and showing how a step could progress the other way- from completely led to not touching, with parallel movement.
When I muve forward toward my partner, I am leading something. But she has to know dance well enough to know that. When you get into more and more complex movements, like the variations on this website, they have to be learned. I can still lead into it, but partner needs to know what I'm doing based on having learned the step. So that's clearly something other than strict LEAD AND FOLLOW. It's a little like "let's do this" and have fun with it. And that IS dancing.
I think tho that when EVERY step of the dance from start to end is planned, then it becomes a set piece, and it is no longer spontaneous dancing, but is a pretty showcase routine. If you dont feel that that is dancing, then I guess it isnt. (But I'd love to be able to do it.....)
Jerry