Steve - couldn't agree more about the way english is taught ruining the enjoyment of it, with unappreciative pupils just mouthing the words. My kids and grandkids say the same! No doubt school recorder lessons have a similar effect musically! But unlike these schoolkids, we play in sessions and other gatherings because we love the music, or at the least want to find out about it. We just don't always have the facility to immerse ourselves in it in our daily lives.

Why did I say "approximation", and approximation to what?
First I should have said "an - inexperienced - player learning by ear";(help - how do I do Italics??). This player is simply copying what those around are doing. Their style of playing has not yet been shaped by exposure to a "tradition". But because they are copying more experienced (one hopes) players, their playing appears more "authentic" than that of the inexperienced who learn from dots. In either case it will be a while before the traditional style/interpretation becomes a natural part of playing. Some of course have "done it right" (as you say) and managed to be born
into a family where everyone plays in a traditional way, so they grow up regarding that way as normal (and probably go off and do something completely different, as kids do!)
I'm sure this applies in every musical tradition - eg how long does it take for "pop" groups to learn to sing so exactly out of tune? - perhaps many do it instinctively because they are surrounded by "pop" from birth (I'm not sure if you would call that "luck").
But being brought up surrounded by something is not "doing it right" (although it may be one's parents are doing it right); it's pure chance.

A (say) french person reading Shakespeare would hear the words in his head with a french accent. Doesn't a (say) irish fiddler reading the dots hear them in their head with an "irish accent", just as a "classically" trained fiddler would hear them with a "classical" accent. This works the other way as well, for me at least; I find it very hard not to play unmarked turns and graces in Mozart symphonies! (that's not very often these days). But the key here, I think you agree, is experience and custom, not how we learnt to read.

Anyway, why should we be ashamed of our accents and have to hide them, spoken or musical? (except sometimes in a performing environment, which has nothing much to do with folk music, apart from possibly the tunes; and even then we wouldn't like to be thought of as yet another Dick van Dyke).