I don't know but 15-17 touches a game sounds right so as to not wear him down. He's still south of 195 lbs isn't he? No way Kirk runs him into the ground to make him a Heisman contender. Plus maybe AW has made it known he wants to stay healthy to be drafted early in the NFL next year, who knows.
I just don't think there is much difference in a handful of extra carries a game. With all the practices and everything else a student athlete does, 4 or 5 carries a game won't be the difference between being fresh and being worn down. If he needs to be fresh, give him less carries in practice.