Well, doesn’t the Harappan civilization make a mess out of all this? Tin was nearby, and there’s evidence of bronze artifacts in all kinds of houses across the cities, and in general less evidence of hierarchical power, and certainly nothing like the concentration you see in other Bronze Age civilizations. We don’t have the civilization surviving as is to the Iron Age, because it depopulated before iron smelting became common. But it’s odd to make the claim bronze had to lead to stratified societies. Clearly, not always.