If a collector had asked, I could have provided my own insignificantly varied version of "Reuben James," which I've been singing - mainly to myself - for sixty years.

Since I learned it from print, and no one has expressed any desire to learn it from me, I don't suppose we can call my version "traditional."

But suppose I'd learned it from a live performance, determined the correct lyrics from a book, and taught it to somebody else twenty years later with minor changes.

Would that make "Reuben James" "traditional" in any meaningful sense?
Obviously any song can be passed on by word of mouth. That's how I learned the first stanza of "The Old Folks at Home" from my grandmother. She thought it was called "Way Down Upon the Suwannee River" - the "folk" title.

That song had an author known to many but not all singers, is p.d., and was passed on to me orally.

Is "Suwannee River" now "traditional"? Yes or no, what does that tell us about either "The Old Folks at Home" or the nature or meaning of "tradition"? I'd say nothing really. The style of Foster's song isn't much like Guthrie's, which is indistinguishable (to me) from that of many anonymous (as well as some signed) American songs.

If we're grouping songs, I'd say style and form are at least as important as considerations of authorship and transmission - neither of which are intrinsic to the song itself.

Since not everyone can be canvassed, moreover, we'll never know even relatively the number of people who learned any "traditional" songs "orally."

I'm far from up to date on recent scholarship, so forgive me if the above thoughts have become irrelevant to current thinking about "folk songs."