I agree the particular combo I was discussing is likely not very useful when compared to just directly virtualizing macOS directly, except in niche cases. One

I agree the particular combo I was discussing is likely not very useful when compared to just directly virtualizing macOS directly, except in niche cases. One such case, however, is when the user is already managing Linux Docker containers for other parts of their development or testing workflow and wants to manage macOS containers with the same tooling. That’s legitimate enough, especially when it ends up supporting nested virtualization of the same architecture and not true emulation, to keep the performance penalty modest enough.