California requires warnings about metal concentrations on virutally ALL FOOD
No, it doesn't. There are two requirements for labeling. Individual food items that require labels have to have them, and anyone shopping can see that only a tiny fraction of the items are labeled. There's also a requirement that the entrance to the store have a label if any food item requires one. Since most food stores carry at least one item that requires a warning, almost all stores require one. That might make you think that all food requires labeling, but that impression is incorrect.