It seems to me that Dave has read into that quote quite a lot of stuff that isn't really in there. All Rumncoke seems to be saying is that music keeps on changing as it goes around, and always will. Which seems commonsense to me. It gets written down or recorded, and that's a valuable way of preserving what was played or sung at one particular time and place, maybe by the person who made it up, maybe by someone passing it on.

But there's no reason to assume that that is going to be the end of it - it never has been in the past.

There's a quote from Sydney Carter I had occasion to post in a frecebt thread which seems apposite: "There is nothing final in the songs I wrote, not even the words, the rhythm and the melody. This is not an oversight; I would like them to keep on growing, like a tree. They have a form, I hope; so does a tree. But it is not fixed and final. It must develop according to the time and place, it must adapt itself to soil and weather." Some songwrites don't see it that way. But that's how it sems to work in practice.