Nobody is saying pick him based on what he has done for the u20/21s so that comment is ridiculous. The reference to the U20s was in response to your original question posed which was why is he getting more patience than Bolasie. The point being he has potential if we can develop him, whereas Bolasie is what he is.
I'll say again, at this stage he isn't ready to be a regular starter in the premier, but he does need regular game time at that level if he's to develop. This would involve starting some games but mainly used as an impact player off the bench.
As regards his game time under Allardyce, no I don't think that he was given enough. Those 6/11 squads consisted of one start along with the other kids in the dead rubber in Cyprus, a game in which he excelled by the way. Another 30 minutes in the FA cup game against Liverpool, in which he also excelled. Plus 2 x 20 minute cameos from the bench. There were other games against the likes of West Brom and Bournemouth that were crying our for a player like him when he wasn't even in the bench.
And are you sure he forced through a loan move away?. My understanding was that it was Allardyce who wanted him to go on loan, the player just forced through a move to Germany rather than the Championship. And the way the manager then treated him in the press was nothing short of a disgrace.