Please understand that the vision system in a Tesla isn't like your vision system. There is no AI which is constructing a model of a 3D world out of 2D visual data, with a road surface and 3D objects located within it. There is no human or higher-mammal level of comprehension of the scene. There are probably a series of algorithmic tricks that enable the car to determine in which direction the distant road is. The computer can then meld that information with the other shorter ranged sensors in the car that do return distance data.

The reason why things like LIDAR are used in self-driving cars, is that these systems can numerically build a model of the 3D scene without having to have an AI reconstruct a 3D scene out of 2D camera data. They return distance information, so the data starts out as 3D, so far less interpretation is necessary. In all likelihood, nothing in a Tesla understands what a truck trailer is, so how is it going to interpret that set of 2D optical data as an object that's like a moveable wall suspended a few feet in the air? There's probably only a rudimentary notion of obstacle in the software.