Rapid changes in my Dynamic IP Address

Yep, this is a mess,  I do not think it is intentional, rather a misconfiguration of NAT64 device, or faulty firmware for said device that has been rolled out to Minneapolis region first.  Again, your IP address is NOT really changing..  However at the NAT device within T-mobiles Minneapolis core, a new source IP address is being utilized for the NAT translation for every new outbound connection.  Another possible reason would be that they have deployed a set of NAT64 devices behind a load balancer, and your traffic is being "load balanced" to a different NAT64 device with each new connection.  In any case, traffic from your real IP address, if it needs to be NAT'ed, but be NAT'ed to the same outbound side source address for every new connection, otherwise it breaks a great many sites on the internet and renders the internet gateway unusable.

It is easy to confirm that NAT is taking place, by using your t-mobile phone hotspot, and look at the the IP addresses that have been assigned by DHCP to your phone. (The internet gateway does not appear to let you see this information).   Go to any of a number of hosts that display your IP and note that the IP address the site reports, is not the IP address assigned to your phone.   Go to a different site that reports your IP address, note that it is different, and also note that your phone's IP address has not changed.

Mike