Well, that's not really the author's advice, considering that he writes:
"I wouldn't recommend quitting your job like I did. Especially, if you have an idea only. Test it first. Most probably, you have a lot of 'hidden' free time so you can test it while keeping your day job."
If your point is that bootcamps generally are waste of time and money, and you suspect that the author just wants to promote his bootcamp, then that's a different thing of course.
Learning to code at 40 to leave your 9-5 job is the worst advice one can give to someone.