I wonder myself. In my community, there are a few that bring it (YEC) up, but a lot that "go along" with it, but I suspect do not really think it is true, but will say there is a young earth and literal global flood etc. just because it is expected to be a member of the community. A little different, but sort of like the pro-life position to be a Republican, pro-choice to be a Democrat, though we REALLY do not want to go there!
I'm not sure how you would ever tease it out to see how many really have those core beliefs, though I think there was a study done years back (with Biologos as a sponsor as I recall but could be wrong) that came up with about 11% of American evangelicals who had really firm feelings for the YEC position. I'm too lazy to look that up but sure someone can correct me if wrong.
I would think that the best thing is to not worry too much about it, as I suspect most are like your friend who would just rather not talk about it, probably because of the cognitive dissonance it brings up. Quite honestly, my wife is sort of in that boat where she accepts an old earth but it really is not something she wants to discuss, as it would put a barrier between her and her more literal friends.