As for fantasies - well, I was fantasizing about the girl down the street when I was 13. It starts pretty early for guys, (...)
I don't mean to sound snarky, but how many guys did you talk to about their fantasies? Because in my experience, pubescent/teenage boys don't exactly discuss their sexual feelings freely, and when they do, they do it in a crude and, in a way, extremely guarded manner. Maybe that's different outside of 90s Poland, but based on what I've read over the years, that doesn't seem to be the case.
My point is, what you write implies is started pretty early for *you*. And you seem to extend this to "guys", and I can't help but wonder how many conversations you've had with other men to confirm that. Because otherwise, you're extrapolating from your own experience, and that's dangerous. Especially since (in my experience) men are conditioned to fit in, in terms of sexuality, so even when the topic *is* for some reason breached, there's a good chance a man will conform with (what he thinks is) the norm. And that skews the perception of what "typically" happens. A lot.
And in fact, the conversations I had with my peers in Junior High or whatever seems to confirm that. Conversations around sex were very awkward, very guarded and very focused on showing off what we felt would prove we were knowledgeable about stuff (not exactly very conducive to genuine sharing of experiences). Not to mention exraordinarily sexist, but that's another conversation.
Or to put it another way: going from "that's how it happened to me" to "that's how it typically happens" is a very big jump. And even then, the jump from "that's how it typically happens" to "that's universally true" is an even bigger one, especially when there's a cultural incentive for men to stay quiet if their own experience doesn't fit the mold.