Here is a visual representation of the collision box for the carpenter’s bench
The green box I have highlighted here represents the invisible collision box. This box tells your character when it runs into another object (or when to stop an arrow from flying through, etc). Ideally, you want to keep collision boxes at a low poly count, meaning, each rectangle you see here, the fewer of these that you see, the better. This helps with performance. You, the player, may not see the collision box, but your computer still has to render that information.
But you also want to have it accurate to the object, otherwise it can be, and is often, immersion breaking when the collision box is off. Which is the result you see in the above screenshot. I, the modder, what I would do is create several sets of rectangles so that it was more accurate to the model. One for the stool, one for the step, one for the bench, and etc. This does increase the poly count though, which for my own mods isn’t really a big deal. Funcom has to weigh these kinds of decisions more carefully though. Collision boxes can impact performance as well as gameplay mechanics as a whole. Even moving things an inch could blow everything up, you generally don’t want to mess with established collision boxes unless you have to. Luckily I’m a modder so I can stick my tongue out and do it in such a way that I don’t have to worry about stuff like that, but Funcom does.