“Autonomous trucks” aren’t truly autonomous. For example, this article says an “autonomous truck” was automatically dispatched by software.
However, the truck couldn’t have gone out unmanned, since it would be illegal (also impossible with current and foreseeable technology). So what seems to actually have happened is that the truck was parked in the private space outside the warehouse, and it came itself to the loading area. That private space is a limited and controlled environment, and yes, technology can produce vehicles that can go on their own in such environments.
This is why we could possibly achieve autonomy on the motorway. Not with further improvements on vehicles—we are already there—but with tweaks on the road.
In less controlled environments, we can’t achieve autonomy.