There has to be some other radar signal for a moving leo's car or bike to detect your speed. His car's speed must be in the equation somewhere.
I've looked at the BMW R1100RT-P patrol bikes with front and rear Stalker Ka units and the only thing that gives them speed is a manual cable to the speedometer head. The Stalker doesn't appear to be wired or cabled into the bike for speed determination at all. That's why I am assuming there is another signal from the radar unit itself that needs to be subtracted from the head-on speed used to get your speed verses his speed (e.g. head-on speed - leo's speed = your speed).
Thinking about it, to hardwire into different vehicle's computer system or mechanical speedometers would make installation more difficult as well. Their car unit must be doing something easier for installation.
The hand-held radar guns wouldn't have the feature, but the vehicle ones must if they are moving.
Right or wrong?