Apparently you can still wipe and reset and reinstall the phones even with "OEM unlock" switched off. At least, we managed to pull it off. But it took about half a day of trying and retrying random things from threads on forum.xda-developers.com. Sorry I can't be more specific, it becomes a bit of a blur after the 5th time :-p
If you do a reset from recovery and not the settings app it locks it down with android factory reset protection and the phone is bricked until the original owner enters their google password.
Oh that might be it then, they still had their google account (or the TFA backup codes printed). Either way it seems sensible to do the OEM unlocking, just in case.
Still stupid that it can brick the phone if you don't have that password.
