A new version of the 7.0 manual was posted in My Tesla, and it seems that the description of the "HOLD" message when AutoPilot is engaged has been updated from the generic "Model S has fully stopped and you must tap the accelerator pedal to resume cruising at the set speed" to this more lengthy description, which tells us that the camera can indeed detect pedestrians (and some nondescript objects):
Model S has fully stopped behind a vehicle it was following but a pedestrian or object was detected in front of Model S, causing Traffic-Aware Cruise Control to be in a HOLD state. Tap the accelerator pedal to resume cruising at the set speed.