Not because it was a "nice guy" at all mate . Because he knew if you went to court you would have won, by giving you a 15-30 k over he knew it would be less likely that you would fight it in court, thats the real reason .
Unless he followed you and checked your speed that way .
The silver eagle radar he used to check your speed SHOULD'T be used in traffic and under their guidelines( police) shouldn't be used if more than one target is within 200 mts , remember thats their guidelines.
I doubt you ever will have such conditions on Anzac bridge, even if you do other things efect the silver eagle radar's reading( mobile phones, other transmiters , even electricity wires).