Well, I wonder if Leadbelly knew or cared whether his windjammer was tuned 12 TET, Wohltemperiert, "just" or "Cajun". I doubt it! Same goes for Amédé and the rest.
But it's interesting stuff for sure! I'm going to dive into that on some ol' rainy day!

Apart from all that, just a question: who started that "dry" tuning in Cajun/Creole music and when?
When I hear Amédé or Iry Lejeune, the accordion sounds "wet" , but with Lawrence Walker it's suddenly almost "dry". Was he one of the first?

You can hear that change from wet to dry not only in Cajun music, but also in French musette (from "musette" tuning to "swing" since the forties with musicians like Gus Viseur) and in Irish traditional (from Joe Cooley -wet- to Jackie Daley - in between- to Sharon Shannon- almost dry.)