I agree a lot with #3 but disagree heavily with #4. There are canonical examples of PhD theses that became successful companies, not to mention the dozens of companies who exited (e.g. CV companies to Qualcomm).
The examples of successes is both anecdotal and survivor bias, you have to look at all attempts and weigh all the successes against all the failures.
There will be future successful businesses based on theses, among the many more failures. The advice here is really aimed at people who think that a great technical solution to something automatically makes it marketable, which includes many thesis authors.
Someone who's done their real market due diligence, and knows which thesis to productize or which problem to solve, they have a good business idea. But for most PhDs, the advice is good advice -- don't sink all your time & money into a business based on your idea if you haven't done as much study of the market as you have on your thesis topic.