It's tracked by Google even if you never visit a page operated by Google. Non-Google websites that include Google tracking are contributing here (which is most of the web).

The sentence you cite suggests that it's "just" such sites that see your activity, while it's a third party (Google) that does as well and that is the issue here.

Sure, technically you could argue that the tracking is "part" of the website that you visit, so it's technically still "only" the site that's tracking you. But let's be honest here, no reasonable non-hair-splitting non-geek would read it that way.

That's true regardless and not the issue. The issue is calling it 'Incognito Mode' and implying it offers the same privacy protection as other browsers' private modes, like Firefox's private mode for example, when in fact it doesn't. It's a standard feature on modern browsers and Google intentionally misled it's users that Chrome offered a comparable feature. Users had understandably assumed Chrome's privacy feature did in fact provide the same level of privacy they would expect from other modern browsers. It would be like me selling you new brakes for your car and telling you there is always a possibility brakes can fail when in fact they didn't work to begin with and would have never stopped your car. One is common sense advice, the other is fraud.

google tracks your incognito tabs just like it tracks normal tabs, without you even visiting google.com