Yeah, `pkg-config` is the Freedesktop original, `pkgconf` would appear to be a re-implementation. Your distro installs `pkgconf` and links the original command to it so existing scripts will work, if they happen to conform to what `pkgconf` considers "correct".
If an existing script fails because it depends on some edge case in `pkg-config` tough. And very aggressive about it they are, "if someone insists on fixing such a non-bug, this constitutes a violation of our [Code of Conduct](https://gitea.treehouse.systems/ariadne/pkgconf/src/branch/master/CODE_OF_CO...), which may be addressed by banning from this repository".