I had heard that most of the greyshirts have spring birthdays and are young for their class, so they are 6-12 months behind developing. The birthdates aren't up for the ones that just came in, but a quick look at 4 from the year before show birthdays in January, March, May, and June (turned 18 the summer after HS). Not saying its planned, but it's probably a consideration that there's a chance they may have more growing to do.