Cap'n,

I am merely extrapolating your argument that singers should only be judged on merit, and not be subject to categorisation, to its logical (and rather silly) conclusion.

The converse of your argument is that if the BBC collectors had only concentrated on "really good singers" they would also have missed a lot of "really good" songs. This is because, with the best will in the world, several of the singers that they collected from were not "really good singers" but sometimes had "really good" songs.