"What we know is that the vehicle was on a divided highway with Autopilot engaged when a tractor trailer drove across the highway perpendicular to the Model S. Neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied."
That's really disingenuous. There's no way to know for certain what the driver did or didn't see, but there are a lot more salient features for them to go by other than the white trailer, like the fact that the cabin has driven across the road or that the wheels of the trailer were square in the driver's lane. A much more likely explanation is that the autopilot set expectations too high, the driver was not paying attention (like in all the youtube videos of the system in action), and the autopilot failed and crashed into the truck.