So miners self-selecting to not mine BCH is proof of BCH mining centralization? I assert that is a useless definition of 'centralization'.
Mining centralization is proof of mining centralization. The market doesn't prefer it.
Bitcoin Cash and Bitcoin Core are equally centralized / decentralized. Think about it. How could they not be? They both draw from the same pool of miners, the same pool of investors, the same pool of users, the same pool of businesses, and the same pool of developers.
The differences are the Bitcoin Core has the advantage as being what the layperson thinks of as "bitcoin" and what most of the infrastructure is currently setup to interface with. Bitcoin Cash has the advantage of low fees, reliable confirmation times, and the ability to scale to a global payment network.
Time will tell which version of bitcoin will win.