Yes. For a while now. Actually to my detriment because TM hotspot users are usually IPv6 only. Which is a real issue for me. When I'm on a hotspot, my customers are unreachable to me. I can't VPN into them because 5 of 6 wireline ISP here are IPv4 only.
Are you trying to VPN directly to IP addresses instead of DNS names? Or using a custom DNS server? You should still have connectivity to IPv4 hosts, it's just that you need to translate the IPv4 addresses into their corresponding NAT64 IPv6 address (which is usually done for you by the T-Mobile DNS server)