You missed the most important part: the site provides something for free.
There's no "if you want to keep learning check my book/course". It's not a funnel entrance, it's not adversarial to you as a reader.
I really really miss being able to enjoy content keeping my guard down, not wondering what is a scam, astroturfing, political propaganda...
I would totally buy his book, even if it was only an offline copy of his site.