was it true that he did not credit his sources

It is not. All the sources in 'Folk Songs from Somerset' are credited, including Louie Hooper. There are no sources named in '100 English Folk Songs', which I think consists mostly of highlights from the same Somerset material. All the singers in 'Folk Songs from the Southern Appalachians' are credited.

I haven't actually listened to it yet, but if this claim is actually made then I fear the worst.