Supposedly, reversals only happen when the evidence is clear the initial call was wrong.
Both reversals which went Nebraska's way were questionable. On the catch, they gave the Nebraska receiver credit from the moment the ball hit his hands; IMO, his foot was off the ground by the time he clearly controlled the ball.
On the 3rd down, Mo was rolling over the Nebraska defender, not on the ground. By the time his back hit the ball was past the line to gain.
IMO, replay officials routinely ignore the standard they're supposed to employ in making reviews, they routinely treat the original call as irrelevant.