This vaginal cuff is the tightness we men feel when we penetrate, and it has lots of nerve endings.
No, it almost hasn't any nerve endings. Of course, not enough to sexual stimulation.
If they were lots of nerve endings (as you say) at the vaginal cuff, women will be in an agony of pain during the last 4 months of pregnacy (due to the pressure induced by the growing foetus and the extreme tension and enlargement of tissues caused by it).
Ask any woman what she does when she wants to reach an orgasm.
They rub their clitoris with their fingers, instead of hitting his cervix introducing a dildo.
In fact, look at most porn movies: What are most girls doing while those big cocks thrust heavily their pussies and asses?: they rub their clits with the fingers, because only the stimulation provided in the clitoris (including is internal prolongation known as "g-spot") and labia can lead a woman to orgasm.
Ah, I've also studied Medicine.
And, also, I'm not fluent in English. That's because I'm Spanish and it's not my native lenguage. My modest level of English was self-adquired.
Pero seguro que yo hablo Español mucho mejor que tú.
You're not the only one who had studied at the University (and don't forget that here in Spain they are some of the finest Medicine Universities at Europe).
And there's a fact that you should know: less than 23% of women reach orgasm by penetration alone according to several studies (including Kingsey and more recent ones).
Ah, one more thing: female pornstars simulate orgasm in porn movies. This is a fact know even for those without an academic degree.