> It only says the first Bay Area SFH law, in Berkeley, was championed by a guy who didn't allow property to be sold to blacks. This is not compelling evidence for SFH being a channel for racism in any subsequent cases across different cities.

You're underselling it. The first US single-family zoning law, not just first in the Bay Area.

Yes, maybe all of the subsequent single-family zoning laws that spread across the US were for totally different reasons than the first one. Personally I find that unlikely.