That's a good question -- for the manufacturer of your networking adapter. Have you checked that the adapter is configured to use DHCP? I agree that it should be the default, but some manufacturers may have other ideas.
Answering my own question:
For clarity, 'Thunderbolt Adapter', is a Networking Connection generated on Windows for a TB3 AIC.
If a DHCP server is run on the same host with the AIC card, then the Thunderbolt Adapter can get a DHCP address.