However, the question is whether the reason you mention is a valid one. I believe a better one is that police officers stay home when they are supposed to work. In which kind of profession do you not get fired when you refuse to (show up on) work? Especially when there is unrest and violence on the streets, you are more in demand; your services are needed even more. In such times, staying home is akin to being a deserter in time of war.
I do not understand how one gets away with that. How do they? What is their leverage?