@jsrptn - It's illegal to show complete nudity (fully visible genitalia) in Japan. Even in pornography. I make the assumption that this person is indeed making these shoots in Japan given the name listed. If that's true, then it's either this, or the pixel blur that nobody likes.
@Golkar Vast majority of these lewd cosplayers are from outside Japan. Sayo Momo is Vietnamese for example. For some reason a lot of top lewd cosplayers are specifically Vietnamese.
So in short, most of these cosplayers could go full nude when they want. Question is, would it be as appealing for the paying fans? Who knows.