>>280317653
I once heard it was some sort of artist health problem. It might have been something that improvement would require taking a lot of time off, but I'm not sure about that either.
LN chapter lengths vary, but the manga is currently in the middle of volume 6 of 13 so far, a new girl appearing roughly every 2 volumes up to 5 total. Later parts of the LN start making a larger number of changes from the WN that has been passed.