well dungeon just doesn't wanna to die ya know? any living beings ain't just lying down to die. so tricking humans to think it is dead so it can relax alittle and not doing anything for long time.
it doesn't seem to be aggressive too.
Just a speculative WAG, but they might of had a brief hiatus or event that prevented them from making a full chapter release. Then added bonus pages to each part as an apology.