It's really tunable and some stores are tuned to "Fort Knox" where even a fly landing UNKNOWN ITEM IN BAGGING AREA.
Others are so loose that you don't even have to take things out of your cart, scan and pay and go.
Others are so loose that you don't even have to take things out of your cart, scan and pay and go.
It uses your rewards card to determine your “risk”, I think. Just a theory. But whenever I’ve gotten a new card, they come check my bag a lot. Then after a dozen successes or so, they stop checking so often. Then hardly at all.
One of my friends forgot to scan an item once when they checked, and he had someone come to check his bag way more often for a while.
Given that "just walk out" apparently means "replace cashiers with offshore video analysts" I'd wager Whole Foods might do something similar and policing shrinkage in self-checkout is too expensive compared to just keeping track of cheats and throwing the book at them if they make a habit out of it.