I was trying to understand the perspective of the article, and that gave me the major clue.
RDPD is one of many books that basically says the key to financial success is real estate investment.
For a few people, and at certain times, maybe, but it is better for most people to make it a (small) part of a wider financial investment plan.
Your first house (or any house) should be first and foremost though if as a place where you will live, and “primary residence as investment” is almost never a good thing.