Might be due to the artists, maybe? Hickman wanted only one for each mini and it's on a bi-weekly schedule of six issues for both Silva and Larraz (Silva is faster, but his artwork is looking so clean that I think they wanted him to give it his all). There's also the fact that maybe editorial hadn't settled the plans post HoX/PoX at the time of the relaunch, so they might have needed a bit of a stall.