With super, the slink version was a separate NMU for frozen, while that version was already in unstable. So the changelogs are different, and they are differnet compiles.
With sgml-tools, I can find only this oddity: Suggests: bsdmainutils Optional: groff, latex, dvips, texinfo, info-browser It uses the ancient "Optional" keyword. It looks like dpkg merged that with the Suggests, whereas dpkg-scanpackages lets it override the Suggests. Richard Braakman