I don't understand what you're asking really but I would say that your friend sounds a lot like me.
I have never understood the need to share every aspect of one's life with friends or even family, I don't think in my almost 70 years I have ever 'opened up' to anyone, even health scares I have always kept to myself on the principle that if it gets seriously serious then I might have to tell them but until then it's my business and mine alone.
When we lived abroad and 'socialising', horrid word, was expected I did that was expected and quite enjoyed it.
After working in a school for almost 20 years, on the day I retired I walked out and didn't even go into the leaving do, I loathe situations that might put me in the metaphorical spotlight.
Probably people think I'm an odd ball and stand offish but I can live with that!
This is probably the most I've ever said about myself, the anonymity of the keyboard!