I think maybe I'm miscommunicating the point. Yes, if overtime isn't needed people should be sent home. Hospitals agree on this; they don't want to pay overtime if it's not needed.
The issue I'm pointing to is that sometimes it's "needed" because of a bad process, like when there is redundant work. Sometimes it's needed because the system needs slack to compensate for disruptions in system dynamics. Sometimes it's "needed" because "that's how we've always done things." Point being, if it's needed, it should be because it contributes directly to better patient outcomes rather than bad processes.