Shimrod,
I dont think that is what Bob Lewis meant at all.
Boundaries will always have grey areas.
In the world of folk song,for some people this includes music hallsong.
I think Bob was referring to music hall songs,not to your examples.
I do accept that sometimes categorisation is unavoidable,but the cateogory referred to here,has in the opinion of Bob Lewis
meant that fine singers have been missed.I agree with him.