The claim (as I understand it) is that power was centralized because tin was rare--i.e., had to be imported via sophisticated trade routes, which presumably could be controlled by the state.

In an area where tin is abundant, individuals could easily forge their own bronze weapons, thus making it harder for the state to have a monopoly on high-tech weapons.

So I think the Harappan actually reinforce the theory.

> which presumably could be controlled by the state.

yes, kiln-roasted Linear B in Mycenaean palaces... built on a giant fault line (literally as well as figuratively)

Civ VII 2.0 should bring back Sid's palaces in monolith data centers like The Machine / Samaritan (note: i am only halfway through season 4)