"Could the same be said of John Cowan ten years earlier? "
Absolutely, John Cowan was a huge part of the sucess of New Grass Revival, and the newgrass movement... which in my view was 20 years ahead of it's time, but they were never accepted by the traditional crowd, or the second generation bluegrass crowd, at least not how the Seldom Scene were. Was just too hard-edged I think... but then again, that mellow, folksy thing wasn't the fence NRG were swinging for anyway.
The generational/demographic wedge probably had much less to do with his Fender Jazz bass, and more to do with that incredible voice.

Now I gotta' go look for my New Grass Revival cds...