I Tried to wipe a Big Sur machine, expecting it to re-install the OS and connect to MDM.
The 6 digits worked. it rebooted to the no entry sign. An internet recovery didn't work (both with newest release keypress and default release - it was orignally a Sierra machine).
In the end the only option was a USB bootable Big Sur re-build. It did rejoin the MDM correctly though.
Anyone else seen this - is this how it's supposed to function? Seems odd.