It isn’t panning per se, it’s more like balance, but filtering. It’s not designed to pan a mono signal in the stereo field, it’s for filtering a stereo signal with more control of the stereoness, if that makes sense.
When you patch a mono signal into the L input so it goes to both sides you don’t get a sense of it panning around the stereo field, you get a left signal and a right signal and the controls effect how they’re filtered relative to one another.
Regarding how it compares to the QPAS, it’s quite different but has some similarities. This is more like a “normal” filter but with stereo control.