Of course you shall never take photos or video, holding the camera, while driving.
But I can see nothing illegal with mounting the camera and let it roll while you drive.
A news photografer in Sweden used to do that. Caught a lot of car chases that way.

The Police do it . . .

Typical attitude from the boys in blue.

Dont do as I do, do as I tell you. If a camera set whilst stationary off road, is allowed to run without drivers involvement, whilst he is on the road, why should it be more dangerous than one in a police car, which is single manned and to which they keep referring to give other officers details of chase speeds etc.

And why do many still blatantly not use hands free, nor even leave the radio work to their partner when there is one alongside the driver.

Because they are better drivers?. Don't make me laugh.
Maybe they are above the law, not really, just above their station too often.