Let's lay this to rest please. It cannot be denied that Bert was very knowledgeable on a wide range of subjects. From a very early age he spent many hours in libraries reading about history, literature and politics and for a while took part in whaling and the Australian outback.
He was also a respected journalist working with the BBC and Picture Post before they decided they didn't like his political stance.

The only quibble that we have with Bert's scholarship is that he didn't make clear the boundaries between his creative abilities and his scholarship, and when it comes to folk music this casts doubts on his scholarship. The ultimate effect of this is that whenever we come across a song that has passed through Bert's hands or a pronouncement he makes on the history of folksong we have to go back and find more reliable sources to verify what he has written.

Exactly the same principle applies to the published works of Percy, Scott, Pinkerton, Jamieson, Buchan, etc., yes, and even the highly acclaimed Motherwell.