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…
I don't wonder about their numbers, it's obvious their numbers are good for them. What I wonder is how are they getting away with something that is clearly illegal.
As already explained, in properly implemented GDPR survey, it should be equally easy to accept, decline or ignore tracking, with the default being decline if user doesn't give explicit consent.