Halfway agree with you. Because it also restores the customization that has been done by the OEM, such as the wallpaper, as well useful tweaks such as the hybrid sleep in the SP3 (system goes to hibernation after 4 hours, not available in vanilla Windows install). Always nice to have the OOBE feel, especially when you live in a country where OS piracy is commonplace.
In addition to that, I have seen a video from the team (I think it was Konsta) where he flashed a pre-cooked Windows image on the V, instead of vanilla Windows, so I believe there is some customization in there.
Finally, while Windows Update can get some of the drivers, the OOBE experience is still far inferior with vanilla Windows, as it usually doesn’t include the graphics driver.