Is not more difficult at byu which is the point I actually made and you discounted.

Hard to have any evidence other than the fact byu has had quite a few academically ineligible players over the years. Also byu is more competitive academically which produces harder courses in terms of attaining grades because the distribution of student achievement is tilted further than most state schools who have to meet certain admission criteria based on non achievement based factors

Also you could argue that having far more players take two years off from school makes it harder to achieve qualifying grades