- set up a new empty site, listed absolutely nowhere, on quite dedicated hosting.
- open it in Chrome.
- a couple minutes later, observe Googlebot appearing in the visitor logs of the site.
Lastly, if you go to the ‘My activity’ settings on Google, you can see: “Include Chrome history and activity from sites, apps, and devices that use Google services”, which I guess can still be dissected further. And I have some website visits from 2016 listed there: including Wikipedia, which doesn't seem to use Google Analytics currently (not sure about 2016)—though these could be visits through Google search.
Also, text in the linked tweet directly says that Google tracks users on third-party sites through Chrome.