When Safari says it blocks or prevents a tracker, what it means is
that the ITP algorithm has flagged some domain as having
cross-site tracking capabilities, and Safari has, among other
things, stripped it of its capabilities to carry cookies in
cross-site requests, also known as third-party cookies.
This is what Safari means when it’s prevented a known tracker in
google-analytics.com. That domain has been flagged as a
cross-site tracking domain, and Safari assigns certain protective
measures to any communications to and from that domain (you can
read more about them here).
Apple’s current UI description for this feature sure makes it sound like Google Analytics is being blocked.