CLARIFICATION:
The Nebraska WR was probably forced OB. The ref threw his hat, signalling the player OB, but he reported to the other refs that the WR was forced out. In his opinion, the WR didn't go OB by choice.
The replay review:
1. ...was called to determine whether the WR had reestablished himself inbounds before catching the ball. He did indeed.
2. ...was not to determine whether the WR was forced OB. THAT IS NOT REVIEWABLE.
So, the review refs did not get it wrong. If a mistake was made, the official nearest to the play made it.
Best explanation I have heard about this. Thanks Chech. E-cred worthy.