> The thing about density advocates which I don't understand is why they wall themselves off to the irrefutable, unquestionable, fact that the second anyone, anywhere in the world, has enough money they move to a less dense area.

That should continue to be legal. You should be able to buy the kind of home you want. That what overturning Euclid V Ambler would allow again.

> I also lived in Japan for several years. The very first thing people do when they get enough money is move out into a single-family detached home in an American-style

What's important to note is that Japan greatly liberalized their zoning, setback, parking requirements after their big housing crisis, and now a family in Tokyo earning median income can actually afford to own a home in the city. You can't say that about New York, San Francisco, London, etc.