There’s no genitals, or even nipples. Oversight or targeting PEGI 12 and less games only. Probably the later.
I was surprised to see that such a good tool is so biased due to American prudishness, which is the only explanation I can find. You can’t even alter the breast size of females.
Also, textures are with forced underwear, as far as I remember. It is ridiculous.
Anything else aside, I’m pretty sure the current Metahuman Creator is not even finished, much less meant to be a standalone, one-size-fits-all solution. It’s labeled a “preview”, after all, and more than a few of the hairstyles note they don’t have assets for anything other than LOD0.
Most folks I know using Metahuman Creator right now in a preview state are generating assets which they then either alter in Blender or Maya, or where they’re taking the head (or even just the hair!) to put on character models generated elsewhere.
It’s probably the case that it’s very uncommon for that kind of stuff to be shown in games so there’s just not much demand for it and it would be low priority for features.