I have figured this out! I have the answer to all Mac products after 2017... The features is disabled by the T2 security chip. You can lower the level of startup security and then Wifi Spoof will work. I have verified this works! I have spoofed the MAC address for a travel router and an Apple TV and logged into web authentication protected wifi systems... See the below link:
https://support.apple.com/en-us/HT208198

Eric

Wifi spoof not working!
Use the rule, get message saying address not changed. Address remains the same.
Manually change MAC Address on main screen, immediately changes back to Hardware address!