Sharp got the idea of using that mode system from Lucy Broadwood.

The idea of describing folk music that way dates back to Glareanus, 400 years earlier. He thought it didn't fit very well. He was right.

You can't make sense of any European folk idiom without taking account of gapped scales. They've been part of modal theory in Indian music for a few centuries, and Bartok was using them to describe the music he was collecting at the same time as Sharp. They give you much more useful information.