Funnily enough, the scene in the movie is impossible to recreate, as the truck uses a flatbed and chains to tie the logs together. However logging trucks have the metal railings on the side for a reason: if they don’t exist, the logs would simply role over anytime you try to stack them, making it much more of a hassle than to just use a dedicated bed for logging.

Even if the sides would fail, the logs would simply roll off to the side and not bounce back due to inertia and friction causing the logs to only move sideways at the speed of the truck rather than backwards.