It depends on exactly what iteration of Autopilot he was using. I'm not sure how old this case is. Early on it was little more than traffic-aware cruise control with lane holding. If that's what he was using then it has no knowledge of traffic lights or anything else and it was a 50/50 chance when you hit an exit if it would take the exit or stay in lane once it lost lane lines.

There's lots of things the media has called Autopilot.