I have no info but the guy worked his tail off all his life to PLAY QB and now he might feel like he's looking at a 4-year Seneca Wallace in front of him. I wouldn't blame the guy for wanting to go somewhere to play.
Don't blame him for wanting to transfer, but why not after the season is over so he can still help the team in case of injury, in addition to getting more practice/coaching to improve his own skills? With our history of QB injuries, who knows if the team may have needed him again, particularly as much punishment as Purdy is taking in the pocket as well as when running?