I would most certainly socialize any dog I had! Being kept in a kennel and only let out for training sounds horrible to me!
I really looked into Schutzhund myself, met and followed the club for a couple of days to see what it was like and all of the dogs there, Rotties, Doberman, GSD's, were all very friendly and playful when they weren't out in the field. They were very focused when actually on the field but all played and sniffed together after and before.
I would most definitely question this.