We know the "real reasons" from first principles - the people tasked with upholding the law have taken that as a license to flout it. Everything beyond that is a window dressing of politics, unfortunately necessary to rally outside pressure for these corrupt institutions to be reformed.

These statistics shouldn't need to be publicly done by independent groups, but could easily be done confidentially by the police departments themselves to avoid having to pay out compensation for their employees' crimes. Alas, police forces find it easier to double down and shirk off liability for the damage they cause, so here we are.