Whether he wanted to redshirt or not doesn't really matter does it? If they aren't going to play him, they should redshirt him. Then... maybe if he doesn't go pro in 2 years he has the option to come back for a 3rd and increase his draft stock.
I would imagine Tanner also didn't want to stand on the sidelines this year and hold a clipboard while he watched Taysom Hill lead them to the Poinsettia Bowl.