I am retired LEO, and my experience is no officer would want a magazine disconnect safety. First the idea that during a fight for the officer's gun, he would be able to somehow be able to press the mag button, to drop the mag, so the gun would not fire, is unlikely. He is fighting for his life. He will do all he can to retain possession of the gun, as he knows he will "die" if he loses the gun. How is he going to push that small mag release button? It is hard enough when you are holding it in a normal grip position, not fighting with all your strength to keep the gun. Could the officer release the mag, sure it is possible, but he also could regain control of the gun, after releasing the mag, and now his gun will not fire.
Second is many officers have pulled their guns, and had the mag partially drop without knowing it, not completely drop out, but enough that if the gun had a mag safety, they could not fire the gun. How many officers would want to carry a gun, and worry if the gun is going to fire? This is the same thought as people that don't like a manual safety. They carry with the safety off, but worry it could get accidentally bumped on, without their knowledge. With either scenario, a pull of the trigger and the gun would not fire. Without the magazine safety, if the magazine partially dropped, at least the officer could fire one shot, the round in the chamber.
There may have been, and are still some Departments that think a magazine safety could save an officer's life. But over time the issue of the gun not firing when needed is much more common than a struggle for the gun. I have seen numerous occasions, during training or qualification, when an officers mag partially dropped. After "fire" is announced, they look pretty stupid when they point and pull the trigger and only get off one shot, as the mag partially dropped out. In a life or death situation, I prefer one shot to no shot.
I have read some of those stories, on how an officer was saved by dropping the mag. I say stories as I do think that is what they are, stories not fact. Has a mag safety ever saved an officer's life? I would bet the answer is yes, with all the thousands of incidents over a struggle for the gun. But again for every one life saved this way, how many other situations have happened because the gun would not fire when needed?
As far as gun safety, who is leaving a gun lay around with no magazine, but they forgot that a round was still loaded in the chamber? The gun should be secured and fully unloaded. If proper gun safety rules are followed, a mag safety is not needed.
Bob