Something that's come up in the foxtrot discussion is the way in which many moderately high level dance teachers know how to dance with two different, conflicting techinques. There's what they do when they are dancing to win competitions, and there's the somewhat uncomfotable way they dot their i's and cross their t's when taking their ISTD membership exam.
The thing is that if you look at the really, really top dancers, it turns out they are using something even closer to classic technique than what most adopt for their exams - yet they are winning with it.
The obvious answer is that most who study the formal technique pick up the details, but not the implication of what you are supposed to do between them. If you take the exam technique details and graft them onto common competition practice, you get something that looks and feels uncomfortable, so no one dances that way outside a teaching or certification setting. In contrast, the classically trained couples that win with that style dance in a way that naturally connects the exam technique details - they don't use their foot that way because it's in the book, they use their foot that way because they dance in a way that makes their foot want to do that.