Comment 1 for bug 1759532

I believe you are seeing a DHCP Client Identifier instead MAC address; netplan's
networkd backend defaults to using this as the client ID instead of MAC.

I think you want to switch to using MAC as the DHCP client id:

[DHCP]
ClientIdentifier=mac

https://askubuntu.com/questions/987673/how-to-get-netplan-on-17-10-server-to-work-with-a-windows-server-dhcp-server