Here's what the manual says about this driving situation:
"Traffic-Aware Cruise Control cannot detect all objects and may not brake/decelerate for stationary vehicles, especially in situations when you are driving over 50 mph (80 km/h) and a vehicle you are following moves out of your driving path and a stationary vehicle or object is in front of you instead. Always pay attention to the road ahead and stay prepared to take immediate corrective action. Depending on Traffic-Aware Cruise Control to avoid a collision can result in serious injury or death."
The issue at play here isn't so much that the car is really bad at tracking parked cars and stationary objects out of view (that's a separate shortfall of Autopilot to get into), but that Tesla isn't making it clear to its drivers that the car can't handle or anticipate this fairly typical driving scenario.
In an email statement, a Tesla spokesperson defended using Autopilot appropriately and reminded drivers that the onus is always on them, even when using the semi-automated tool.
"When using Autopilot, drivers are continuously reminded of their responsibility to keep their hands on the wheel and maintain control of the vehicle at all times. Tesla has always been clear that Autopilot doesn’t make the car impervious to all accidents, and before a driver can use Autopilot, they must accept a dialogue box which states that ‘Autopilot is designed for use on highways that have a center divider and clear lane markings,’" the statement read.
Autopilot doesn't mean you can just sit back, relax, and take your hands, eyes, and mind off the road and wheel.