Or use something like GKE where the containers should be running directly on hardware, so you only have one layer.
Doing a little research: GKE runs on https://cloud.google.com/container-optimized-os/docs/ which is designed for GCE, which runs on KVM: https://cloud.google.com/compute/docs/faq
So it looks like just Triton and Red Shift.
Disclaimer: I used to work at Red Hat, which means I like the people behind Red Shift, but that also means I hate the people behind Triton as part of the early 2000s Linux/Solaris wars.
I'm 99% sure that Google runs one VM per container because that's the only way to make it safe.
Anything else would be insane.
I'm 100% sure you are wrong. You might as well just use VMs.
Containers are not only about safety, you know.
Hypervisors are much, much harder to break out of than a Linux container.