I'm sure there are some people who are attentive enough about traffic before they start studying for a learner's permit (at 14 most places, I believe, not 16) to be described that way, but many are not. Especially if you live and go to school in a suburban area your experience with traffic is probably largely a) crossing not very busy streets, b) riding a bike on, again, not very busy streets where traffic laws are honestly barely obeyed anyways, and c) getting on a bus or being driven everywhere, at which point maybe you pay attention or maybe you don't.

There's definitely going to be some osmosis but I think you're pretty vastly overstating it (and including several years in which your ability to even comprehend what traffic is is going to be severely limited).

That's not even remotely true. When I started learning to drive I had 0 experience with traffic. When I was fully licensed I had less than 2 years experience.

So you had literally never seen a car or crossed a road before?