>>3058621The actual law for obscenity in Japan is so open to interpetation that anything can be pegged as "obscene" and it's open to interpretation whether the law even applies to fictional content. In actual enforcement, obscenity is basically understood to be unobscured depictions of genitalia in sexual situations these days.
Cases like what you posted are just publisher self-regulation. There are two general rules of thumb:
1. More explicit content helps sell volumes
2. More explicit content in a volume is less likely to get in trouble than a serialization
There are probably lots of cases where English speakers are given the less explicit version, but there are also cases where the English version is more explicit than even the Japanese volumes (Ero Ninja Scrolls aka Arakusa Ninpouchou, for example). With so much content and disparity between platforms it's really confusing nowadays to find the most explicit version.
