IIRC, and someone please correct me if I'm wrong, I don't think they release date and the registration date are connected. In the past, results would come out after the registration window opened. And in some years, some States released near or after the registration window closed for the April exam. *cough* Pennsylvania *cough*.
SE always follows PE, but that's because the SE grading is more labor intensive and takes longer. I seem to recall someone on here or reddit, doing a historical comparison of PE and SE release dates for April and October. I *think* they saw a pattern, but I don't recall if it was a strong pattern or not. I've never tracked SE released patterns and don't have a feel for it.