Comment # 1 on bug 960251 from Wolfgang Bauer

First of all, PackageKit is not a KDE application. KDE only provides a frontend
to it.

But yes, it is on purpose that it behaves differently than YaST->Online Update.
The latter only installs official updates ("patches") from the update repo like
"zypper patch" does, while PackageKit installs all available package updates in
the configured repos like "zypper up".

That's by design.

You can configure it  in /etc/PackageKit/ZYpp.conf though, set
HidePackages=true to make it work like YaST->Online Update.

Also, as PackageKit (and its zypp backend) is completely independent of YaST,
it does of course not respect YaST's settings. Although I even think that YaST
doesn't remember this setting itself anymore in the latest versions, i.e. it
only applies to the current session and is not saved.

If you want to disable installation of recommended packages globally, configure
that in /etc/zypp/zypp.conf (solver.onlyRequires = true) This should affect
*all* package management tools that use libzypp, including PackageKit.