You have a better perspective so I concede.
My opinion came from dealing with cops in various unsavory neighborhoods throughout SoCal. There, they just arrest everyone on both sides of the accusation. “Mutual combatants” or some such.
What you mention in SoCal could be more on the subject of gang investigation, where police have overwhelming evidence that certain people are involved in gangs.
But think about it. Someone tells a cop who wasn’t present that you slap them, and the cop carts you off to jail. That’s a system ripe for abuse.