Interesting! That might account for American variants in my collection such as 'The Butcher Boy' and 'The Social Hop'. However do you have views upon the possible connection to 'Picardy Third' as described above. the major ending to a modal tune seems to be a great deal more widespread than I realised.

Rigby, The Hammonds collected from George House of Beaminster, and I took the same song and loads of others, from his son and Grandson in 1984.
By the way please take and sing any songs that you want from the collection. John K. and Pete and Barbara Snape sing a few, but there are plenty of others for the taking. All yours.