For example, this is a job for a seasonal door greeter at retail, by definition it is temporary. Even if it wasn't meant to be temporary, is someone who is "overqualified" really more of a statistically significant "flight risk" than some high school kid, an elderly retiree, or someone who somehow has made a career of being a seasonal door greeter?
I suspect all classes of potential hires would be very nearly equally incredibly unreliable in the long-term for a job of this ilk, if you actually hired from all groups and did a study on job longevity.
Its a little different from skilled trades or silicon valley programming.
So the average employment length is a year, but more realistically the "old" first shift people work there about four years and the kids and seasonal work there about ten or so weeks at most, its not a smooth bell curve.