Well I didnt watch the game, but you arent allowed to do that as a defender. A lot of times in Football both the WR and CB will be jostle with each other for position and the refs dont call it if no one is going overboard, but in this one the only hands I see are from Utah. I think the ref would have held the flag but at the very end the Utah CB pushes off. You can see the Utah CB put his hand on the WR, then turn around and push off when he sees the ball coming to the inside.
The CB definitely had position on the WR. If the CB had tried to make a play on the ball instead of pushing off at the end, nothing would have been called. The WR did a good job of trying to make a play on the ball to sell the interference call. Was it a weak call, yeah, but the CB had no reason to use his hands, he already had great position, just make a play on the ball instead of holding.