I’m beginning to think this is just how it works, MT get DHCP assigned addresses from ISP and uses a dynamic DHCP server to serve one of these to the downstream. So there is no NAT involved (well other than the CGNAT in this case), but I’m effectively grabbing 2 IPs from the ISP. Maybe this is fine, but it’s not clear from the doc if this is actually the case?
This is how it works.
What leads you to believe you are getting two IP addresses from the ISP? The MT LTE device gets a single IP address from the ISP and passes that through to the downstream DHCP client.