Just a guess: team prestige goes up (or down) from year to year based on the freshmen you recruit. If they are increasing the OVR of some freshman, particularly 1 and 2 star guys, then they have to tune team prestige to not inflate just because the freshmen ratings are higher. A team full of 1 and 2 star guys is still bad, they don't gain a prestige star just because they are suddenly getting guys that are 4-5 points better.