Sorry, I know this is confusing. The Geograph genitalia isn't the issue. It's the UV map the NGV8 expansion creates called 'genitalia' that's the problem. Even if you remove NGV8 from the model the Genitalia UV will still be there covering the lower torso and thighs. I simply don't know how to get rid of that UV or return to the default genesis uv mapsSo you're talking about the geograft genitals themselves?
Can't you just delete them from the scene object tree? the genitals should be a child of the G8.1F object.
I know I've successfully done this for the "headlights" nipple grafts and "dicktator" male genital grafts on G3 and G8 models before.
(Apologies if I am completely off track... I don't actually have Daz v4.15 / G8.1 installed yet due to issues with the version so I can't actually test to try to reproduce your issue)