@CheerTheDead
they didn't think up part by part but have full chapter storyboard prepared that artist and editor agreed beforehand
then as schedule is monthly by contract, artists have to draw and send work as much as they could to update manga on time, so they just split chapter like that from full chapter's storyboard and become c1.1 c1.2 c1.3 ... something like that
this monthly schedule is need, to keep work schedule in pace (if you just make it as artist send work when they done that will become bad habit for work)
, to make reader stay in touch with manga because a flow could die out if it disappear too long even if they're popular manga
(ex: HxH, World Trigger, they stopped by artist's need and that really effect them as you can see now)
well, if artists could finish their full chapter in a month that would be ideal and I think they work+train with this work period to reach that point so they could be full-fledged mangaka