[putting on "raised by historians" hat]

The key phrase above -- whether in the general or specific case -- is "with all the relevant information at hand". The great trouble with history is that the body of available information is forever changing. Archaeologists find new tombs in the Valley of the Kings, divers locate previously unknown shipwrecks, family journals turn up revealing information about historical figures or events that wasn't previously known.

The shipwreck example is relevant here in the Pacific Northwest; something over a year ago now, researchers published new findings regarding an early shipwreck near Neahkahnie Mountain on the northern Oregon coast. The fact of a shipwreck was well known, but there'd been speculation and guesswork for most of a century as to the ship's origins. Finally, though, enough specific evidence became available -- and the technology for analyzing it got good enough -- that it was possible to reach a reasonably firm conclusion. This is, of course, important from a historian's perspective, but it also forces the re-examination of a lot of entertaining local folklore involving reputed buried treasure.

I rather think something similar must have happened in the current author's case, since it's evident from their story that a number of other performers clearly shared the same understanding of the tale in question that the original songwriter did. But that's a theory...and I need to head off to work right about now.