If it didn't sound literally true, it isn't. It's a joke based upon a stereotype.
It's also not literally true that the crime rate is so low here because any potential robber of a liquor store is related to the cashier.
It's also not literally true that "This here's mah sister-cousin-wife Mary Lou" is a common introduction.
Front porches have been known to collapse here without killing even one blue-tick hound.
To my own knowledge, we can't all give skin grafts that take permanently.
We can't all count to twelve without taking our shoes off because of the 6-fingered hands.
I could go on, but you get the idea. It was a joke.