For clarity, because the obnoxious ones out there didn't get it, this refers to how Arch, Debian, Fedora and most other distros just default to systemd and hence can (and probably will) make use of run0. While, on the other hand, distros like Alpine, Artix, Devuan, Void and others (including *BSD-systems) will not. For distros with no defaults (e.g. Gentoo), the user gets to decide.