The situation is symmetric if there's just a getter and a setter for a state variable, but perhaps sometimes temperature() does a measurement and there's no way

The situation is symmetric if there's just a getter and a setter for a state variable, but perhaps sometimes temperature() does a measurement and there's no way to set it because it isn't a controllable quantity (for a thermostat I can set my desired temperature but it will take time for the room to warm or cool to that temperature).