They do exactly this with their case studies. There are several linked in this post: https://www.strongtowns.org/the-growth-ponzi-scheme
https://www.strongtowns.org/journal/2011/6/14/the-growth-pon...
1. That itself is not great. There's no compelling reason for the government to subsidize things that way. Why deliberately push a form of development that's horrible for the city finances? Modern zoning rules usually force that kind of thing to exist, for no good reason. This is one of the things strongtowns talks about.
2. Some cities don't have a dense core with enough activity to subsidize the sprawly areas.
You wouldn't even be blocking sprawly development if that's really what the market wanted. You would only be allowing more dense development. Which would only happen if the market preferred it.
That's 10-20% of a typical property tax bill. They're fudging the numbers somewhere.