[dijit]

the ini-like format was used a lot on DOS and Windows internals.

Which was a part of the argumentation that systemd is very “windows” in its design (hidden errors, monolithic design).

Definitely an established standard (though not as much on UNIX-likes) before TOML was popularised though.

[self_awareness]

Systemd was modelled after launchd, which is a process manager in macOS. It has nothing to do with Windows.

Launchd uses XML to describe unit files (actually, it uses plists which can be binary, but most of the files are stored in xml).