I’m not aware of any protection aspects related to the hardware-assisted virtualization other than to try and speed and isolate scans.
Perhaps there might be if virtualisation/isolation of a possible threat. I haven’t got it enabled, but I think that the paragraph in the Settings > General > Troubleshooting section would give a good idea.
CPU virtualization extensions Intel VT-x / AMD-V allows us to perform filtering of some low level system operations. It is currently used by sandbox/self-defense/anti-rootkit. The protection is slightly limited without virtualization, but nothing crucial. In most cases there is some fallback mechanism implemented, not requiring CPU virtualization.