This is rubbish. For what were her and Cecil doing if not stultifying a song's development by printing all the versions of the songs they collected?

The idea that a song can only become a folk song if its original author is unknown, is nonsense.

There are many people singing songs, in their own way, thinking they are folk songs without ever knowing when or who composed the songs and so many examples of these songs, where there is an original recording but the current singers are not aware that it was ever made.

Songs are musical statements first and always before they ever become documentary records. They are all open to individual interpretation, in exactly the same way, whether their originator is known or not.