[Cairenn]

No, you are misunderstanding. What it does is scale the world view, moving it 'up' (or down, or left or right) the screen, leaving a blank space at the bottom where the majority of the UI elements are then placed. That way none of the actual 'world view' is obscured.

[edit] The below is not necessarily the best example, since everything is open to show things off, but in the attached image, the entire world view has been letter-boxed/view-ported - it's been moved in from the left and right, and shortened from top and bottom. With the exception of the spell book and the character panel, the rest of the UI elements are sitting on blank space, the world view is scaled down. That way you still actually see the whole world without the UI elements hiding any of it, but it's just scaled somewhat smaller.