I have never had a time in my life when I felt like I had a genuinely attractive body, even when I was only slightly overweight, so I have no way to know what modesty about sexual parts only would feel like. I don’t want people to see my body because it’s not attractive. But that is the only reason: if I had a nice body, I would have zero problem with being seen completely naked. Or rather, the fact that I was seen “in the bits” wouldn’t bother me in and of itself - I was never uncomfortable with my bits being seen by my gynecologist, for instance, and I’ve heard of many women who find it “embarrassing” and I don’t comprehend that in any way.
The only thing I can imagine would make me uncomfortable about strangers seeing me naked would have everything to do with context: I wouldn’t want my bits seen if in the seeing it could easily be construed by others as an invitation; I can understand feeling vulnerable to unwanted approach and contact. (While I theoretically support the idea that a woman should be able to dress in any damn way she likes without having to fear that she’s “inviting” rape, including being stark naked, I also think it’s unrealistic to expect that walking around stark naked in front of anyone and everyone would be neutral in the effect it would have on anyone and everyone. So while it might not be fair to expect me to modify my behavior because other people can’t control theirs, I’m less interested in taking a stand than in not being raped.)
But outside of that I can’t really imagine for myself how a woman with a pretty body that she feels good enough about to show off in a tiny bikini would be embarrassed by people seeing the tiny bits under the tiny bikini, and maybe most of the women who feel comfortable being in public in tiny bikinis really wouldn’t be, I don’t really know.
I havent’ done a stellar job of making this clear, but if you think you can offer me some enlightenment on the nature of modesty that is exclusively connected to the sexual bits and has nothing to do with feeling unattractive or with religious expectations, I welcome it.