Unless you can prove beyond doubt that they are the earliest form of the songs

But what evidence could possibly prove that?

I used to have an interest in UFOs and why it was that some people thought they'd had contact with alien beings. This discussion reminds me a bit of a debate about the common features of alien-encounter narratives. One side argued that stories from different times and places were too similar for them all to be fictional, so they must have a real origin. Other people (self included) thought that what we were looking at was a stock of folkloric motifs, which cropped up in different stories through cultural transmission. The point is that the evidence is a perfect fit for *both* interpretations; you just have to go with what you think is most probable.

Steve's argument here is that the flowery language, stock images and standardised turns of phrase that we see in a song like this are characteristic of broadside hackwork. Which is true - but aren't those things also precisely what you'd expect in songs coming out of a predominantly oral songwriting culture? I suppose we only really know that oral transmission has been at work when we can compare a collected song with a written original, but I don't think that entitles us to assume that the direction of transmission is always print to oral, or that nothing with any level of polish can come out of tradition.