Windows can be used to enable the "feature" Hyper-V, but then you have to reboot, which bootstraps Hyper-V AND then Windows. Other VMs added are running in parallel to Windows, on top of Hyper-V. This is even true for the WSL2 kernel if you enable WSL2 in Windows. Windows is just giving you a convenient management interface to the other VM.
These days you don't even have to enable the GUI in Windows server. You can run it completely in Powershell on Hyper-V. That's been true for years.