In KDE neon we are running appstream-generator over our archive which includes many old builds. Appstream-generator seems to take the oldest build in the archive and ignore newer ones. This means fixes to the appstream files don't get used.
http://build.neon.kde.org/view/mgmt/job/mgmt_appstream-generator/97/console
18:59:05 2016-11-02 18:58:51 - INFO: Processed minuet/16.04.3-0neon+16.04+build8/amd64, components: 0, hints: 1
But minuet is on 16.08.2-0neon+16.04+build17 which includes many fixes in the appstream file.