Comment 61 for bug 336634

If you think pkg-config is not designed correctly, please bring the discussion to the pkg-config list. Or look in the pkg-config archives since there have been many discussions on Requires.private.

http://lists.freedesktop.org/mailman/listinfo/pkg-config

The fact of the matter is that fedora can't just change the behavior of the tool because it's inconvenient. Although there is no formal specification, what I've described is the expected and stated behavior of Requires.private. It can't mean one thing on debian and another thing on fedora. That makes the tool useless.