Admittedly I didn't check the non ISO method, rather expected it to be similar, but isn't.
Looking at the two scripts to run on an existing Windows 10 installation, the only thing I can see it bypassing is CPU & TPM.
Someone in the comments has suggested adding this value in the registry, currently it's only noted this worked for the beta:
"BypassSecureBootCheck" in HKEY_LOCAL_MACHINE\SYSTEM\Setup\LabConfig
I will try the other scripts tomorrow on a VM, see if I can get it working.