They may say it there, but my first encounter with "youins" and where I consistently hear it today is in....east Tennessee. My wife is from an upper middle class family in Knoxville and I don't hear her say it as much. But my brother-in-law in Sevier County sure does.
Yes, you’re right, it is used in East Tennessee.
From what I have heard the East Tennessee accent is in a class by itself. they say ‘bewk’ for book, in other words pronouncing ‘book’ to rhyme with ‘boo’. East Tennesseans do sound a bit like Lowland Scots, or the ‘Lallands’ dialect.
A beautiful style of speech BTW.
I have a copy somewhere of several pages from a court reporter’s transcript, from about 1990, so not at all ancient, filed in Washington County, Virginia — very close to Sevier County, TN — where the term is written as “youens.” Also, the word “yous” appears several times.