Not to say BYU hasn't had issues with their S & C, but it shouldn't be surprising that Povey got better at combine drills when training specifically for them.

IMO, training players for the combine and training players for a football game are different animals with different objectives.
Preparing players to score high at combine drills won't necessarily lend itself to great football performance.

BYU should be more worried about minimizing injuries and maximizing football game performance, not shaving seconds off cone drill times.