Lil What I've bolded describes it very well. With these people, instead of shared knowledge and experience bring you closer and making them ACT PUBLICLY as if you're closer, they almost seem driven to act out their independency and prove they haven't fallen under the influence of the closeness. Lil, I see some of my independent behaviors in this line of thought. Sometimes being very independent and other times only being a little independent.
One thing I can add is I act independent so I don't appear clingy/needy to BB, under BB thumb, or trying to be a suck-up so I can get something I want later. When a couple has issues with each other, I see why they are not close in public.
Maybe other guys have other reasons for acting independent. Maybe other guys didn't act as independent as your bf. Having issues when in private and together, then meeting friends, for me it is refreshing to talk with other people.
BB and I don't socialize with that many different people and when I am out, I want to meet and chat with the people that I have something in common, or share some new ideas.
After an event is over, BB and I fill each other in on what we as individuals talked about with the other person that wasn’t there and part of the conversation.