The manual doesn't say you can only use at full throttle I would suspect, so even if they could they couldn't discard a warranty issue as mis-use Very few use the as they are meant to be: on what ride do you get full throttle on the road these days?
Mine works (up and down) at most revs seamlessly. The only time it seems to have a hiccup is if you forget what you're doing and come off throttle on an up shift (which is understandable!).
do you skid before or after the wheelie? If you turn off the electronics, its more likely the latter.....