Here's the use case:
I play music from my iPhone to my TCL TV via AirPlay in the evening. I then lie down in bed and eventually decide to go to sleep.
If I just stop the music on my phone, the TV stays on all night showing the AirPlay screen saver. Instead I have to step back into the living room and turn off the TV manually.
It would be nice if the sleep functionality worked if AirPlay is on, but not in use.