It's changed because they had a different artist doing vol 3 and 4. I think they decided to have them done simultaneously with different manga artists. Releases are still slow though (but it probably would have been slower had they stayed with consecutive instead)
I love this manhwa tho, it feels so fresh! Also the story is enjoyable. The characters are not like you know born from one mold characters like other manhwa, it feel fresh and new.
It's more realistic for monks to have one sided love and give up on that love than actually pursuing it and won(?)
I feel like it just nice, now we can say that we have almost all kind of story