Turning off the camera power would mean it wouldn't show up on the bus, so the computer wouldn't know it existed. It would make sense for the camera itself to

Turning off the camera power would mean it wouldn't show up on the bus, so the computer wouldn't know it existed. It would make sense for the camera itself to drive the LED, instead of the computer/drivers doing it. I don't know if the camera ICs support this or not, though -- if not, it's not really something Apple can add if they're integrating a standard camera component. On the other hand, they control the T1 entirely, so they can easily do this with the new architecture.