The author's consent form is very simple and isn't using any shady UX tricks to get the user to consent. One action will opt you in, one action will opt you out. I wonder what results you would see for something like yahoo, the daily mail, reddit, or other sites that heavily rely on ad revenue, which attempt to force the user to accept the cookies through non-obvious no buttons, or long processes to opt out of cookie…
Why would anyone consent to be tracked if given a real choice? What are the benefits? The 9% look like an error.
If tracking means the website I enjoy get more money out of me, and that I get better ads for it, I'm all for it. For website I don't enjoy, I agree completely, I wouldn't share anything with them, but I would also try to avoid them, so essentially, I do that naturally consent or not.