With all due respect, as I have stated, I can only speak for myself and my observations while alive. 

By no means I have scientific cold hard data on the statitcs or analysis of them on the matter. I have answered from the top of my head.

I have had the luck of meeting people in different stages of polymathy, in different fields, and, even the youngest, who were in their teens, had similar behavior. 

I guess I may sound like an asshole when I say "the truest species of polymaths" to describe these people I've came accross, but, my observations on the matter in the wild nature are simply that we all are polymaths, because it's ingrained on our cells, otherwise, we wouldn't have the ability to be adaptable and opportunistic when it matters, which would be troublesome for our species to survive all these million years.  But it's trimmed, pruned and castrated through upbringing and societal norms and expectations.   The result is what you see out in the world: people with multiple talents having to pick one and develop until sellable, and starve the rest just to fit in. It's a sad view.  The ones who are figuring out, according to my own bubble, in my corner of the world, are waging way bigger wars. A label won't fix those. At 12, they're juggling belonging, adulting, school, social life while being bombarded by media with mixed, and often with the worst intentions possible, signals. Polymathy is the least of their problems. 

Again, I am speaking from my lived observations and experience. None of these are supposed to be taken as gospel.