It's my understanding that at the U there was zero chance he'd ever play quarterback. At BYU it's unlikely he'll play quarterback but they're going to give him a fair shake. He was HS teammates with Preston Rex, loves the BYU coaches, and believes BYU is a place where he can develop and make an impact (even if it's not at the QB position).
Given BYU's track record with quarterback development and Taysom's recent success as a dual threat QB, I see the appeal. He knows that it's an uphill battle, but BYU really has done an amazing job of developing walk-ons and developing QBs so it's a win-win for Nick and the Cougs.