I think the reason that the wheeler is just barely taught/covered is fear on the instructors behalf of the student duffing the prop into the ground, with all the insurance and liability and all the legal nonsense that goes on now. I know when I did my TD checkride I got the distinct feeling the instructor was nervous on final (it was his personal plane) and as soon as I completed the first and only wheeler with him having his hands hovering a few millimetres from the yoke, he announced " that's great" and that was the beginning and end of the wheeler portion of the sign off. I knew it was not a great landing and felt he did also, in fact it was just pure luck that I pulled it off.