pkg-config(1) manual page does not document pkg-config files format. The old pkg-config implementation does so <https://linux.die.net/man/1/pkg-config>.
Please provide the file format documentation with pkgconf. Maybe this reverse engineered documentation <http://dev.gentoo.org/~mgorny/pkg-config-spec.html> could is better.
This bug appears to have been reported against 'rawhide' during the Fedora 26 development cycle.
Changing version to '26'.
This is now provided in pc(7) in pkgconf-1.3.90 in rawhide.