Hello
If your unattend.xml file is being ignored during the Windows PE phase, there could be a few reasons for this. Here are some things you can check:
Check the location of the unattend.xml file: The unattend.xml file should be located in the appropriate architecture directory on your WDS server.
Enable unattended installation: In Windows Deployment Services, right-click your server name and select Properties. Under the Client tab, enable unattended installation and browse to select the .xml file for the specific architecture.
Allow image to install in unattended mode: Right-click the image and select Properties. Under the General tab, select “Allow image to install in unattended mode” and select the file.
Check the log files: If the installation fails, you can press Ctrl+Alt+F3 to get a command window on the failed install. Then change to either c:\windows\panther or c:\windows\sysprep (depending on where your unattend.xml file was) and look at the log files in there. One should tell you what happened with your install.
Reference documentation:
[SOLVED] WDS 2016 and unattended.xml - Windows Server (spiceworks.com)
WDS Unattend.xml - create partitions not working - Windows Server (spiceworks.com)