No it's a very similar idea, just on workstations instead of servers. Qubes is built around "do everything in VMs" as SmartOS is "do everything in zones."

It's just a usage detail that Qubes may have a slightly higher percentage of linux containers vs smartos - at this point both are probably mostly linux containers on both OSes in terms of usage. (Qubes can also do Windows vms and they amped up support for this in the latest release, while smartOS has native zones and i believe you can do freebsd and maybe others on bhyve.)

Differences are many, including that Qubes has no concept of a "native" VM (dom0 is just a thin fedora wrapper around Xen) and that the global zone in SmartOS is significantly beefier than dom0 in Qubes, since Qubes offloads networking and usb io and bluetooth and sound to independent service qubes (VMs). And their development has been entirely separate. But they are spiritually siblings. I think it's an inspired comparison.