I know many former players and managers talk about needing game time to develop and the list of loanees that went on to succeed is much longer than guys that hung around the training ground without playing for years that succeeded.
I would imagine that playing in games versus just training helps you develop by facing real situations against real opposition going all out to stop you. I also think that going against defenders more at his level is likely a better development system than having Toby eat his lunch everyday in training. Although if he is a winger there is some argument that going against our "FBs" may actually be easier for him than what he will face in League 1 or the Championship.
Sure he's played tons of football but for most of those games he is likely superior, if not far superior, to his opponents. He can likely get away with stuff that he can't in the PL and beat players based purely on his skill which he won't be able to do in the PL. By playing against players that are closer to his skill level he has to learn to play when he isn't able to just boss people. He has to learn how to adapt, improve in areas and learn new skills to keep up.