On Windows nested virtualization already existed before WSL, all the kernel and device drivers security features introduced on Windows 10, and made always enabled on Windows 11, require running Hyper-V, which is a type 1 hypervisor.
So it is rather easy having to deal with nested virtualization, even those of us that seldom use WSL.
Yes, nested virtualization has existed for a long time... on Intel. On Windows, it is not supported on ARM. For a long time it wasn't even supported on AMD! They added AMD nested virtualization support in Windows Server 2022!
Note that when the Windows host is invisibly running under Hyper-V, your other Hyper-V VMs are its "siblings" and not nested children. You're not using nested virtualization in that situation. It's only when running a Hyper-V VM inside another Hyper-V VM. WSL2 is a Hyper-V VM, so if you want to run WSL2 inside a Windows Hyper-V VM which is inside your Windows host, it ends up needing to nest.
So it is rather easy having to deal with nested virtualization, even those of us that seldom use WSL.