The reason he is picked is because he has a huge (relatively speaking) level of experience, in one of the toughest leagues in Europe, at the age of 20, and is a tidy player who does the simple things well, and is very good at taking instruction and performing specific roles that are demanded of...
Walton in the U-20s for tournement in Holland, too:
http://www.thefa.com/news/england/development/2014/oct/aidy-boothroyd-announces-england-u20-squad-021014