To be completely fair, any kind of sandboxing inside of Qubes's VMs do not mean much, because it is on X11. Any app can pwn any other app lol.

With that being said, yeah, he's being disingenuous as per usual for sure. Part of Qubes hardening is trying to not allowing an attacker to gain root to make it harder to attack Xen, but our evangelist here claims it doesn't matter if an attacker has root :)