I think the art depreciation in the latter half of this chapter is probs due to exhaustion.
I mean from page 13 or so onwards the detailed drawings up until he explodes from the coccoon would tire anyone out. Especially when you consider the time constraints for manga and also generally how people are.
So I'm not blaming the artist for the small but actually detrimental corners cut and lazy drawing in the latter half of the chapter. As time and time again throughout this manga he has flexed his drawing skills and made me feel insecure at drawing even though I don't even draw.