The behavior I get is whenever there is proper communication with the computer, the pin is driven high.
If the DAC is not properly recognized, the pin stays low. The pin never goes low as a result of being idle.
I. too. thought it might only light when music is playing but that is not what happens.
Also, if I just supply power, the pin stays low.
If you use "disconnect" in the device menu, the pin will go low.