Which is fine -- nobody is asking for a law requiring all housing to be high density. The ask is to remove the laws prohibiting new housing from being high density.

Which should make it even easier to find low density housing, because you won't be competing for it against people who just need a place to live and don't care about having a big yard.

Right. Nobody is trying to force anyone to live densely. The point is: dense housing (e.g., Manhattan) is expensive because of supply/demand. Lots of people do want to live like this. And it's illegal to build this way in most places in the U.S., only perpetuating the affordability problems across the board.