Slightly counterintuitively, Apple Containers spawns linux VMs.
There doesn't appear to be any way to spawn a native macOS container... which is a pity, it'd be nice to have ultra-low-overhead containers on macOS (but I suspect all the interesting macOS stuff relies on a bunch of services/gui access that'd make it not-lightweight anyway)
FYI: it's easy enough to install GNU tools with homebrew; technically there's a risk of problems if applications spawn commandline tools and expect the BSD args/output but I've not run into any issues in the several years I've been doing it).
If you've got an exploit for docker / linux containers, please share it with the class.
What I'm saying is that in practice, containers and VMs have both been quite secure.
Also, you can configure docker to run microvms too https://github.com/firecracker-microvm/firecracker-container...