Hi SansComic so that was you, with a different name?
I just don't think that, as an example, a man who was in a clinic looking for the surgeon would refer to that surgeon as a "boy" (or as a "girl" for that matter). However, lots of people do refer to female bank tellers, for instance, as "girls" but wouldn't refer to male bank tellers as "boys". How people refer to their friends is idiosyncratic, and not really what I am talking about...
This is my experience, and seems pretty straightforward.
It seems to me that we make subtle differences in the way we refer to strangers and acquaintances, based on their sex and the level of authority they have in society.
I haven't read any literature about this (I guess you are implying that I haven't thought of this myself, but have been instructed by someone).
I do think that how we use language is interesting and sheds light on how we think, but I haven't considered this before- it seems kind of like a simple example of mild sexism in society.