The article has somewhat of a clickbait title. The bug was actually in polkit, which is available on every single one of those distributions you mentioned, and is a dependency of a bunch of other low-level daemons. It happens to be an optional compile-time dependency of systemd, but a distro can ship a version with polkit disabled and just use sudo, if that's what was wanted.

WSL is probably very similar to other containerized Linux scenarios, where you might want a small init to function as a sub-reaper within the container. I don't think that is much of a specialized case at all, as far as inits go anyway.