Let's look closer. I believe you are correct, the corner is in a zone. Notice however, he is playing outside and on top of the receiver. That says the zone is a deep 1/3 or it could be man with a single high safety. The outside linebacker took the underneath crossing route which actually looks like a coverage bust. #32 of GSU should have taken the receiver coming underneath but he looked lost. If the pass went to the back he would have had a terrible angle to make the tackle. Slayton could have become a blocker leaving one man to beat for the end zone. Thats just my opinion.