Inital sales at a convention. Intentionally limited physical availability, time constraints in production. Doujin going digital after that doesn't completely counter the dynamic.

These thing are shown from external perspective. Horror convention, sure. Comedic, obsessing with the details would be great to see though.

One way to put it is, it is more important for your beautiful girl to have a big butt for such a concept, wrapped around herself. The artist draws breasts instead of the actual concept. They make the same mistake the story is built around.

I am rather dependent on machine translation, Using Firefox's built in dictionaries, to read it. 漢字は得意じゃないんです。

I can still complain that the manga artist, assisted or not, needs time to study the anatomy more. the first full view of the pose connects the legs in the wrong place.