Making sure applications don't use category icons?

[Dylan McCall]

At the moment, gnome-control-center's .desktop file uses the
preferences-system icon. The preferences-system icon is a category
icon. That strikes me as an incorrect thing to do, because it limits
what icon theme authors can do[1] and (with my web dev hat on) it
feels semantically wrong.
[1] https://bugs.launchpad.net/ubuntu-mono/+bug/921061

Am I right that it's incorrect to use something other than an
application icon for an application? Is this specified somewhere? If
it isn't, I'd like to suggest that it be added to the Desktop Entry
Specification. (And perhaps desktop-file-validate should complain in
this case, too).
The example above really sucks because we have a major distro ditching
a standard icon name because it isn't being used properly.

Thanks,
Dylan