Alright then, enlighten me.
Let us suppose that you have a GPLd application "foo" which links
against "libbar".
You can only distribute the binaries for foo under section 3 of the
GPL, which requires you to provide the complete source for libbar, and
you must do so providing all the freedoms that GPL sections 1 and 2
guarantee. That is, you have to distribute libbar in source, and
libbar must have a GPL-compatible license.
You have one special exception: if libbar is BOTH:
normally distributed together with the major components of the
operating system AND
not distributed along with your binary for foo,
then you are exempted from the requirement to provide the source for
libbar.
You have ommitted the second clause entirely, and it is this which is
most relevant here.
The special exception allows you to ship, for example, emacs binaries
linked against the proprietary HPUX libraries, provided HP distributes
those libraries along with the major components of HPUX (that is, they
cannot have unbundled them), and provided you are not shipping those
libraries yourself.
This is specifically designed to prevent HP from including an emacs
binary which is linked against their libraries, shipping the whole
thing as part of HPUX, and not providing the source for their
libraries.