Yes, WinPE booting is well supported by normal MS techniques BUT if you want to boot from an ISO AND specify an unattend.xml file then it is not well supported (and very confusing too!).
In many versions the XML file is only detected by Setup if it is on a Removable drive.
By injecting batch files into the WinPE X: drive using wimboot, we can run Setup.exe and specify any XML file of our choice.
There is no dependency on having to use a Removable USB flash drive.
Using E2B, you can select an ISO, select an XML file and then let it fly. The XML file can wipe, partition, format and install a specific SKU of Windows and configure it all unattended. When a new ISO is available, just use that instead of the old ISO.