The Army does its block leave so that the Drill's and instructors can see their family and enjoy their holiday as well. It doesn't affect the training IMO, well accept for a few missing home and quitting, but I'm of the opinion of fuck them, didn't need them anyway, better in basic than at the unit.
Besides, Army basic is a fucking joke anyway and is not something to take any real measure of toughness and or meaning. The only two things that were challenges for me in Infantry OSUT was not beating the shit out of the dumb shits the Army recruits and road marching. Everything else was pretty easy, in fact boring most of the time.