Not every age group throws up the same level of talent. AP believes the 16s are a special group and is shouting about it, nothing wrong with that, and they may be getting special attention too.
The players in the 18s who felt they needed to improve have just had a firecracker put up them from the big boss and now the whole group will or should respond to that.
The 20s have already been cherry picked and now only late developers will have a future (if at all). Thats the deal, theres no guarantees and never can be, and its talent/potential related. Its hard but either your in or your out based on that criteria. If a player who was "average" can suddenly start performing then I'm sure he too will be ring fenced, its always in the players hands.
APs total honesty is unusual however I find it refreshing, and at least we and his staff know where we are and we just have to get used to it. personally I really like his open and honest approach. He's not closed the door on any individual but he has given all individuals in the 18s something to think about.