"whether what they are performing is actually traditional or a second-hand retread"

We'll never really know will we? Unless you were actual witness at the point of the collection of a particular song. Then again there is the number of different versions of a song...which was the original and which was "a re-tread"? Sharp collect several different versions of the same song, I believe
I know I'll purchase The Imagined Village regardless of what the liner notes or adverts sayand I will purchase with the same excitment I had when I purchased my original copy(on vinyl, which I still have) of Liege & Lief.