The book was written by finance professors who examined the characteristics of actual millionaires. They found a lot of people who appeared to be millionaires did not actually have a net worth over a million dollars.
High status professional are expected to drive nice cars and live in a big house. It's harder to be a millionaire if you're spending a lot of money.
The authors were surprised to find that a lot of the Americans with a net worth over a million did not fit any of the "millionaire stereotypes" at all. They drive an old pickup truck and drink Bud Light.
I like the Tweet thread, but prefer the Millionaire Next Door cause it's backed up by actual data. It also seems like the Tweet thread is focused on advice that'll get you a net worth in the top 0.1%. The central premise of the Millionaire Next Door is a lot of people have "regular jobs" and get rich (depending on your definition of rich). See the janitor that amassed an $8 million dollar fortune: https://www.cnbc.com/2016/08/29/janitor-secretly-amassed-an-...