Because he hasn’t played well enough to earn that title yet.
He was a TF last year & had both good & bad moments which is to be expected, but he was not the best Safety in the ACC last year. He’s enumerably talented & can become one of if not the best in the conference, but he’s not there yet as of right now...
If the criteria is strictly based on what they did last year, then that title belongs to Chamarri Conner.
If it’s a projection forward, then it’s up for debate with a number of different candidates.