Your right but also wrong. The distance required to safely overtake a large articulated vehicle does indeed rely on line of site, during peak times on the average B road your distance for line of site alone could be up to three times the length of the truck in question. Not only do you need to make up that ground but also pull in safely relative to the trucks speed however slow that may be.
I wouldn't say the driver in any vehicle regardless of size is predictable in their actions, one mistake by a truck your overtaking and your in the ditch