Ralph Peer of Victor was the driving force behind getting the Carters to adapt and copyright everything. Ralph had them copyright everything in AP's name, even if AP had little or nothing to do with the actual arrangement. However, AP split the royalties equally with Sara and Maybelle.

Pardon my heresy, but I personally find the Carter adaptations generally lackluster in comparison to the original works. The originals may have erred (per modern tastes) on the side of the florid and contrived, but the Carters watered most things down to the excitement level of weak tea. While I've first tripped upon some songs due to the Carters, it has never been their versions I wanted to learn. If the Carter sound managed to develop more interest later on, credit is due primarily to Lesley Riddle (who was also responsible for preserving the music of the songs that he and AP gathered during hunts for new material).

The best threads for all things Carteresque are these:
Origins: The authors of the 'Carter Family' songs
Carter Family Songs: Summary of Sources
Lyr Add: Some Carter Family songs.

Sadly, none of them sheds any more light on the origin of the "Hello Stranger" stanza.