I'm not sure what qualifies as wealthy, but most houses in the SF Bay Area bought in the past few years are probably financed with jumbo mortgages. E.g, 20% down on a $1MM house leaves $800k to be financed, which is greater than the $765k criteria stated in the article.
Not just the last few years. Bay area mortgages have been jumbos for decades. When I bought my first house in San Jose for $325K in 1994, the conforming loan limit was $200K.