Frankly, I kind of don't like the analyses that rely on how white a city is. We all know that has been a factor since the Griffiths moved out of DC, but I have to believe that if money were less tied to race and ethnicity in this country, suburban African Americans and Latinos would be as likely or more likely to support attendance as anyone else living in area where kids play the game. Maybe the great number of successful African Americans in hoops and football makes suburban African American kids gravitate towards those games for the past 40 or so years, but there is no shortage of Caribbean and Latin American players in MLB now for kids to look up to. I know that if this guy is competent at regression he's corrected for income, but I would think that if Manfred is a visionary, then he'd view that as a challenge and not a negative.
The issue you raise about Austin, stadium financing, might be why MLB may not want to give them a team and may be why Portland lines up ahead of Austin, but it has nothing to do with how well a team could draw and attract followers. Austin also brings San Antonio on the weekends, at least. It is a separate MSA, but if you look at drive times for Charlotte, you also have to count that in Austin's favor.
As for Sacramento, it would only get a team if Oakland moved away from SF, which you would think SF might like. Sacramento is more Oakland's territory, almost as much as San Jose is SF. Doesn't it more naturally draw from the east side and north of the Bay than SF? Seems more viable than San Jose.