I don’t have too much to add here other than to say growing up with the internet but before porn was free (or at least reasonably accessible with dialup and parents who grounded you if you tied up the phone line) I found fanfic to be a wealth of information.
It was very obvious to my 13 year old self when something was written by a cis male or not based on the descriptions of the sex scenes. There was something about reading a woman’s perspective on sex that made it seem less scary and confusing and even, gasp, fun, that would not come across in male written fic. Because usually the male character did the act and the woman received it.
Similarly, slash fic was informative as well. Like, obviously they didn’t teach you how anyone but a hetero couple engaged in sex at school (and even then, barely). And here were these stories, explaining things you had no one to ask about and in some ways, I think, normalizing those relationships.
I wonder if this is less of their role now because anyone can get on porn hub and look up anything. But 20 years ago? I learned everything I know about sex from fanfic