Why would you bother to spend the time figuring out whether or not it needs to get deployed? Why would you spend time training other (and new) people to be able to figure that out? Why even take on the risk of someone making a mistake?
If you make your deployment fast and seamless, who cares? Deploy everything every time. It eliminates a whole category of potential mistakes and troubleshooting paths, and it exercises the deployment process (so when you need it, you know it works).