The globe article did say that most likely police departments will allow the gun carried on duty by the policeman to be unlocked !
It is a known fact by police trainers that the cop under stress not only would not be able to manipulate the clicking mechanism of the safety [ loss of dexterity under the chemical cocktail] , he might even forget the combination or the very fact the safety is on when faced with deadly force ! That is why cops hate safeties !
The lock would go on when the policeman takes his gun home with him for the night so it cannot be fired by his kids , should they get a hold of it ! Now you can argue , why doesn't he just unload the gun? For the same reason he will forget to put the safety on >> more often than you think when he gets back home ! People tend to get complacent around guns or tools used day in and day out ! The lock may not be foolproof but it is a step in the right direction to reduce some accidental shootings ! One policeman once , awakened in the middle of the night by the roar of a gun shot in his bedroom , and found that his wife had taken his loaded revolver from his holster, he had left on the night table , and had blown her brains out !