Debian package management puzzle

[Ephemeral root <ephemeroot@bluebottle.com>]

How useful is grep-dctrl? Having nothing better to do, I did
some informal tests of the program. The results have left
me even more puzzled about the relation between dpkg, apt,
aptitude and the other upcoming or obsolete Debian package
managers? Can somebody account for the anomaly below? There
are still more wonders I uncovered with "apt-cache search"
and "aptitude search". 

albino:~$ apt-cache show remember-el | grep Maintainer
Maintainer: Sandra Jean Chua (Sacha) <sacha@free.net.ph>
albino:~$ grep-available -FMaintainer 'Sacha' -s \
 Package,Maintainer
albino:~$ grep-available -FMaintainer 'Branden' -s \
 Package,Maintainer | head -n5
Package: xfwp
Maintainer: Branden Robinson <branden@debian.org>

Package: xspecs
Maintainer: Branden Robinson <branden@debian.org>