Interesting. While reading the post, I did not have the feeling this is the main point. But yes, the point is probably equivalent to the measurement of 'concentration' for which you propose the Herfindahl–Hirschman Index and other formulas.

Is there good data out there to use as input for those formulas?

Often when I read about distribution of crypto, the numbers used seem very foggy. Like account balances on the chain. Those could mean anything. One individual might own 1000 accounts (in a wallet). One account might belong to 1000 individuals (on an exchange).

I would love to hear about some rough estimates for different crypto currencies. Like "How much ETH do the top 10 holders hold"?