As far as I'm aware there can only be 5 2003 born player in the youth squad side so some were going to miss out. Davies, Quansah, Woltman, Corness and Blair seem to be the ones picked. Going from being with the first team for a period in the summer to not in this is a bit odd, but with Woltman going he may get added in anyway.
I think he had injury issues which is why he missed a bit of last season as well