I have no answers for you guys. All I can say is that I've seen this truck doing its route for years. Usually the pile is that high only late at night. This must have been an especially good day. By the way, while you can't tell fom the photo, there was a guy inside the pile and making more room. He sounded muffled.
I haven't personally seen this truck, but a few others that does Al can stacked all the way up.
Usually they don't stack up that high, just up to the wooden rail.