The problem, as i see it, is that you can't reliably determine which 17 year olds are going to make it in the AFL, so they collect all these measurements which gives them a big pile of numbers they can pretend is data. That gives the clubs a feeling of control so they can kid themselves that drafting is not mostly done by intuition and superstition.
Using a skinfold test to pick a recruit is very different than a professional dietitian setting a professional athlete a target and then measuring their progress.