Whonix-installer error line 176 (Kicksecure Whonix, updates over tor, and S76 HCL)

No, Qubes really isn’t nested by default.

Nested virtualization means if a virtualizer runs inside a virtualizer.

Whonix being based on Kicksecure doesn’t imply nested virtualization.
Kicksecure being based on Debian doesn’t imply nested virtualization either.

Debian with Kicksecure “running on top” is just a way to say “Kicksecure software packages are installed on Debian”. Not about nested virtualization.

A hypervisor is a software that can run VMs.
A hypervisor is a virtualizer.
A hypervisor is not a VM itself.

One part is commands. The other part is configuration files which I mentioned earlier in a reply to you here somewhere.