It's a weird arrangement (like everything Japan does). Hentai is produced uncensored. That is, the original material, pre-release, is uncensored. For distribution in Japan, the company has to apply censoring to the genitals before release. However, other companies (outside of Japan) have no such restrictions and can sometimes license a hentai release for translation and dubbing for international distribution. When they do this, they can usually get the original uncensored source material, and that's what they use if at all possible.
Sadly that seems to be happening less and less in recent years, so some really good stuff never ends up getting an uncensored release outside of Japan.