ITP now also degrades first party server-set cookies to 7 days where the first part of the IPs don't match. So if you're using CNAMEs for your measurement and the you have a.a.x.x and b.b.x.x it will downgrade.
Wow. OK, so the servers can just proxy the requests. Then what's Safari gonna do? Unless they totally eliminate all state and cookies in browsers, they can't prevent that!