Duke wanted to redshirt Semi. That's not what he wanted. And that's fine.
Duke also wanted him to play the four (like he did this past season at SMU). Semi wanted to be a wing. He wasn't a better wing than Hood, Sulaimon, or even Dawkins 3+ years ago.
Semi left, matured, and soon realized where his greatest strength on the court could be. In a nutshell, it was where the Duke staff pictured him.
All that said, Semi needed to make the best decision for himself. He seems happy at SMU so I'm happy for him.