So this is pretty misleading. It's really a full system emulator (qemu) running inside Docker, using root privileges on the container that make the isolation very weak (--privileged).

It also uses hardware assisted virtualization (KVM) which is not going to be available most of the time Docker is.

You can think of the Docker platform itself as subset of the Linux platform. With many common features removed by default... SYS_PTRACE, cgroups come to mind as not allowed within the container. (This "Docker as a subset of Linux" is also what you end up getting from most "Docker as a service" platforms offered by clouds, including kubernetes. I'm referring to AWS Fargate, Google Cloud Run, GKE, AKS, here.)

So don't think of this as macOS in docker wherever docker runs.

What would be a lot more analogous to macOS in docker would be running Darling in docker: https://www.darlinghq.org/ ... if that could be made to work for the entire system (highly unlikely)

Darling is more like Wine in that it runs native executables for one platform as native processes on another platform using a compatibility layer. Wine, by the way, definitely works quite well inside Docker.

Also, one final thought. I wonder if you could get macOS to boot in QEMU without hardware assisted virtualization. Then you could probably run this in a fully isolated container again. The performance would likely be abysmal though!