As far as I understand these things, reproduction is the primary evolutionary driver. Bonding is secondary but complimentary. I have lots of erogenous zones, but my dick is designed to cum.
Regarding the OP, his theory may have some validity because of the human journey. Most of us left Africa 60,000 years ago (sorry creationists), but 40,000 years ago something happened in the Middle East where we still mostly were. As far as I know most scientists think there was some ecological or climatic shift. Some went back to Africa, some went East and some went north to Europe.
The point is that suddenly we faced different climates and this necessitated for some, clothing. Clothes, particularly skins, cover our natural smells. I think that somewhere deep down, I can still smell when a woman is sexually responsive. This is how most mammals communicate their sexual readiness for reproduction. Smell is still one of our most powerful senses.
There's no doubt genetically distinctive communities of human beings exist and have done for a significant period of time. But the degree of variation necessary for their to be fundamental differences in the way different groups of human female's genitalia is organised did not exist in the time frame we're discussing.
Apart from infinitesimally tiny genetic differences which produce the enormous variety of skin tones, hair colours, facial features and body types there is in fact no real substantial differences between all the different genetic families of the human species.
I share exactly the same organs as someone from Kamchatka (of paleao-Asian ancestry) and exactly the same kind of body as someone from Ethiopia.
There aren't differing ancestral human vagina genes which then coalesced into the genetic stock which now forms the human species.
However, having said all that we do share genetics with other ancient Hominids which are now extinct, the Neanderthals being the obvious example, but there were others. Indeed in the example of the Neanderthals modern humans are thought to have interbred with them meaning that many modern human beings have Neanderthal genes in very tiny proportion.
It's possible that Neanderthals were genetically different enough to human beings to have had differences such as the ones being discussed in the OP, though they were genetically similar enough to produce offspring with us which themselves were able to reproduce. Who knows this admixture of intraspecies DNA might be responsible for the kind of differences the OP is interested in.
Mind you I highly doubt it.