This is useful for the few cases where wheel events are not for scrolling. For example adjusting the volume in the tray.
In this case having the metadata that the delta is backwards is important. From a kwin POV it's just proxying the libinput isNaturalScroll setting to clients.
Tested against "qtbase/examples/widgets/widgets/mousebuttons" with modified Qt and changing the scroll setting in the Plasma touchpad UI.