Speaking as another one of "those kids", I disagree. I became better by doing things, sure, but it was not in any sense an "organized and reflective" practice. It was... just doing things and reading about things because it was fun and interesting (and, eventually, because it paid). But not by deliberately exercising.
Regular, yeah, I'll give you that. Any skill gets better with practice.
Nobody is claiming that practice needs to be boring. “Practice” is just a name for the time you spend playing around at the edge of your ability.
I was one of those kids you're calling out to and I'm glad I had the opportunity to just dig in, but I'm far better at what I do after decades of practice.
The same is true in each of the numerous other skills and crafts I've pursued in that time.
You can write code in no time, but you really are going to only become continually better at it if you embrace organized, reflective, and regular practice of some kind.