No, he referred to a 40 year old virgin in Silicon Valley. In general advancedatheist argues that young people who don't learn the requisite skills of mating when they are young don't learn them afterwards.

I don't see that reference. It's possible it's been removed - the comment/post has been edited - but either way that's both still not the right age range, and a red herring anyways.

Where does the assumption that improving one's sex life is impossible if one already has sex come from? If you believe that sex is bad than you will have less fun with it. It becomes harder to communicate with a partner about what one desires. Plenty of women who do have sex have no orgasms.

Null. Improving one's sex life requires having a sex life in the first place, the absence of which is rather central to his comment/post.