Im pretty sure windows basically runs their ultra mini lightweight "OS" to run their installer exe. Well all I know is that they have their installer.exe that auto opens when you boot up from an installation USB. I had the same problem as you before but I think you should have a look at this page. It might help. And also before you do search up what an "unattended windows installation" is to understand this a bit better.
Heres the link to the website:https://4sysops.com/archives/unattended-deployment-of-windows-7-via-wds/#:~:text=From%20the%20WDS%20console%2C%20locate,xml%20answer%20file