POSIX is probably something closer to what I mean.
As the Joyent branded zone is the native instantiation of the OS sharing the same kernel, there is no hardware virtualization, or rather, hardware is virtualized only once and zones then share the abstraction, as they are just normal UNIX processes. It's a completely different approach than hardware virtualization. One global zone can have up to 8192 non-global zones all sharing the same kernel, and the imgadm / vmadm combination makes the Docker problem become a non-issue.
Note that Solaris Zones predate Linux cgroups by several years, and that Zones offer full process isolation and were engineered explicitly for isolation/"OS virtualization" purposes, whereas cgroups were initially an attempt to give the kernel information about how to share resources between processes, and still do not offer real security separation or process isolation. cgroups is also a moving target, as "cgroups v2" or "unified cgroups" is still just barely becoming usable (CPU controller just added in 4.15, which is only a few months old).
You can run Docker images directly on SmartOS, because Joyent implemented the Docker API, and they also implemented a Linux compatibility API. It's not always perfect, but the fact that it works at all is admirable.
SmartOS also contains the equipment for hardware virtualization, and Joyent has even ported KVM (and recently bhyve) to illumos.
You can, theoretically, manage OS and hardware-virtualized systems at once through SmartOS, similar to what libvirt tries to provide on Linux (though their LXC integration is deprecated iirc).
I am not a SmartOS fanboy and have not as yet deployed it into anything more than a lab setting, but it, along with anything else non-Linux-centric, is consistently ignored for no real reason.