Moneyball, which chronicles the ability of the small-market Oakland A's to compete in a widening gap between the haves and have-nots, is a instructive example of why "conventional" evaluation methods aren't without their shortcomings.
The A's found some innovative statistical evaluation criteria that allowed them to find players that other teams either undervalued or didn't want at all.
Back to BYU. I think BYU has shown the ability to find some undervalued talent. This is because largely due to two main factors
1. BYU has a different talent evaluation methodology that allows them to find excellent players that don't necessarily max out all of the standard "measurables" used by recruiting evaluation services.
2. BYU's primary geographical recruiting regions are somewhat under-served/overlooked by the recruiting services. For example, BYU has several notable 1 star [unevaluated] recruits like Curtis Brown and Fui Vakapuna. This is also compounded because a lot of the recruits don't attend the camps during the summer that talent scouts are frequenting, which often is what gets the ball rolling in terms of their "hype".
BYU, BSU and others have shown themselves as exceptions to the "star rule". Some may attribute that to coaching, but I think it's also largely due to the inadequacies and incompleteness of the current talent evaluation paradigm used by Scout, et al.