Differing lists of packages?

[Martijn van Oosterhout <kleptog@cupid.suninternet.com>]

When I download the Packages files from potato and
then view the packages from the website, it sometimes
seems I'm looking at two different lists.

For example, in the Packages file I just downloaded,
quake-3dfx is listed as depending on (among other
things) libGL1. But the website doesn't mention this.
Similarly, the website says it depends on mesag3-widgets,
which is not mentioned in the Packages file.

What's going on?

The packages file is:
ftp.us.debian.org::debian/dists/potato/contrib/binary-i386/Packages

The website is:
http://www.debian.org/Packages/unstable/games/quake-3dfx.html

Martijn