[riogordo2go]

At least in prior Google Analytics versions, a third party cookie was used, giving the possibility to link you to every site that implements Google Analytics. But Google explicitly states not to do this, so you are correct in calling me out here.

[jhpacker]

GA4 still uses the doubleclick cookie. It also encourages the use of Google Signals and runs measurement requests off of the main google.com domain to help it track users based upon their Google login.