I can understand reasons why KDE desktop is disabled for root, even this is not exactly true. It is still possible to start KDE from console "startx" . This has erratical behavior when wish to close KDE session resulting loosing one console in "nowhere" state. (See my previous post).
I believe that try to lock root KDE login has no much sense. One who working in linux, should be aware of danger. But it is much easier use yast and make other settings and switching to console window to execute some comands, then work from console all the time. E.G. editing some scripts in different cfg files is more easily using Kwrite then VI in most cases. Also when doing something often we need internet browser and information like this to search for. I am happy when can copy and paste "sausagelong" comand from browser to console shell comand line.