Looks like a nice feature though, pleas consider to report it as wish to
http://bugs.kde.org
many other windowmanagers support this, in windowmaker this is called something like "windoze style window cycling", fluxbox supports this as well but i forgot the name of the feature.
another thing, that annoys me, is that the window focus sometimes is completely lost - i.e. no window is focused, and alt+tab does not move the focus over to another window.