Turning off S pen detection?

There's a setting labeled "Turn off pen detection" in settings that can be toggled on/off. Does it save battery life when it's off or on? It says "Turning off pen detection when the pen is attached can extend battery life", so I assume when "Turn off pen detection" is ON it saves battery life, correct?

Also, what does this setting even do? I don't notice a difference whether it's on or off.