Oh, man.
My nephew works for Kroger, primarily picking stock for online orders.
He's a good dude and I enjoy hanging out with him, but I absolutely promise you that he doesn't do all of those jobs. He doesn't do anything quickly-enough to shift roles like that, and never has. To use a polite managerial description: He definitely works at his own pace.
I don't see that kind of task diversity at the store I usually shop at, either.
The register people do register stuff. The self-checkout people do self-checkout stuff. The order-pickers do order-picking. The people who bag groceries and fetch carts just bag groceries and fetch carts. The produce folks do produce. The florists florist. And so forth.
Sometimes I see a management-type range-walking from one problem to the next, but even that's exceptional.
It's the only real grocery store we have in the small city in which I live, so I get to spend a fair bit of time there whether I like it or not. I've spent years passively becoming familiar with the people who work there, and the jobs they do.
If they moved around much between different roles, I'd have noticed it by now.
(It's also a union shop, which may have something to do with it. When high-speed shifts from pushing a broom and heads out to the parking lot to fetch carts before he starts sorting produce, he's taking work away from the people who normally do those jobs and diminishing their roles. Unions may tend to dislike that kind of thing.
We didn't shift around much when I worked in union retail, either. It was a big deal for me to spend a day away from my department to help out with another one that was short-handed, and an opportunity was always presented for me to say "No, I'll just keep working where I normally work."
It was an even bigger deal if they needed help over on the grocery side of the store, which had a completely different union with a completely different contract. The union guys had to agree to allow it every time before that could happen.)