I have the opposite problem.
If I enable the BIOS option “MAC Address Pass Through” iPXE sees that, FOG does not, it sees the USB-C dongle MAC address.
I even tried to recompile iPXE, still the same (I guess it’s not the fault of iPXE?).
The FOG server is version 1.5.9
Anything else I can try?
Machines I tested this on: Lenovo L14 and Dynabook X30W