Many homes are never sold, but are passed from one generation to the next. When homes are sold, they are first offered informally to other members of the community before being listed, so they are sold before ever being listed. If people locally have enough money (able to do an all-cash deal quickly) and if it's a nice enough place to live that local demand exceeds supply, the majority of homes might be sold without ever being listed.

If the home is listed, it is listed with one of a few local realtors, who can very subtly steer certain buyers towards and away from certain properties. Even if legal lines are crossed, it's very difficult to prove that laws were broken. It happens less often than it used to, but it still happens. US Senator Corey Booker has at various times shared this story about his family that sheds a bit of light on the phenomenon:

https://www.facebook.com/corybooker/photos/id-like-to-share-...

I'm reasonably sure the author is just making this up. As a US citizen you have wide discretion on where you live, even extending to several other small nations that have signed agreements with the US.

If you're renting or selling property, most of the discretion that used to be afforded to buyer's is now outlawed. But it would require someone willing to pursue a case if they felt they were not sold a home because of their race or whatever.