I'd go with the "paranoid" part. Your internal-network addresses aren't
reachable from the Internet in the first place. It's the electronic equivalent
of saying that not only are you at 21 Sussex Drive, you're in "Jean's room";
unless you're already inside, "Jean's room" isn't particularly useful
information.
With 4.1, you probably weren't using the proxy at all; 5.1.2 adds transparent
Web proxying, but earlier versions required explicit browser configuration
to use the proxy. The proxy has always provided that information (or, at least,
it did so in 4.1.2, the oldest version I have running right now).
Cheers,
--Rich