I didn't say average, I said it's not unusual. Obviously you need to be good to get to that level. But you can do it without any schools, just by sitting down at home and learning, and then replying to few LinkedIn messages.

In my experience, this would be the case for cca 20-25% of the people I work with. So yeah, definitely not average - but definitely not something you never see. Every team has few devs like that.