I believe the point he is making is that the games can run in the native Windows above Hyper-V and then WSL2 / other Linux installs can be run under Hyper-V from the native Windows OS.
As far as I understood it, Hyper-V is a native hypervisor like Xen or ESXi. So if you're using Hyper-V even your Windows is running as Guest alongside any other Hyper-V VMs and WSL2.