He doesn't look physically anywhere near SL yet. Maybe just an honest conversation was had about first team chances this year? There's no room in the back row if everyone is fit he'd be way down the list right now - Newman, MacDonald, Olpherts, Roberts, Simpson and out of position Handley and Martin might all be ahead of him. If that's the case he would likely have been loaned out all year again anyway, so it might just be better for everyone for him to make a proper fresh start elsewhere, and he seemed happy at York.
Who knows, he may become a superstar but from what little I've seen he's miles off.