I went and checked them all out. There's definite vagina on the miniskirts, and the male loin cloth does have a penis and nutsack. The other female pelvis models though, it just looks like they didn't model in underwear like Books said. As well, you really need to contort the camera to see it in a number of cases. With some models, you can only see it if you fall forward. Falling back doesn't show it.
Personally I'm of the mind that it's not really an issue. I mean, if you walk into an art gallery, you're going to see way more nudity than this. You could go to a library and find anatomy books and get more nudity than this. You have to go out of your way to see the nudity with these models, you need to zoom the camera in and tilt the camera. And it's not really sexualized nudity either. I guess you could argue the miniskirt might be, but, a flaccid dick in a cave man loin cloth isn't sexual. And keep in mind that since you need to contort the camera to see it, most people aren't going to see it in general gameplay since most people look at the game from zoomed out and at higher angles.