Wee little drummer said it:
"If you sing in your natural voice - you have nothing to learn from anybody."

OK, maybe you could still learn a thing or two (like how to project or how not to ruin your vocal cords), but since when is an untrained, natural voice not "folk," even if it sounds unusually clear and resonant?

Is Joan Baez not "folk" because she doesn't sound like Buffy Ste Marie or Tracy Chapman?