The author is actually correct. A lot of this had to do with community and housing association bylaws that forbid selling to non-caucasians outside of San Francisco and Oakland. After the civil rights law changes in the 1960s, minorities began moving into areas that still had these bylaws in place, which were now ignored. Many of those bylaws still existed into the 1970s before they were removed. Daly City's Westlake neighborhood (borders San Francisco) still had the bylaws forbidding non-whites in the 1970s, when asians began moving into the area. Now it's mostly Filipino.
Those laws were overturned in a 1948 Supreme Court decision.