Nah, it's just really heavy competition for space there. Sometimes you get accepted, sometimes you don't. Holding a booth in the previous Comiket helps, but if you don't apply in time or don't have anything new to offer, you lose your spot, I imagine.
He was there last Reitaisai selling 2 books. What is actually the criteria for joining Comiket? Especially when it is so huge and space is probably limited?