That’s not what’s happening. Hyper-v is a type-1 hypervisor. When it’s running, even your Windows instance is running within hyper-v. Windows 10 has the hypervisor platform that lets other vm developers hook into the hyper-v host architecture, that’s how you can get android emulators and virtualbox running under hyper-v. It all works fine but is a little unintuitive to set up.