The 3D dimension provides an additional data point: nesting level.
I have to agree. My first thought was going to be to disagree because I always just use something like view formatted source or something to look at my nesting levels within the dom but having it show nesting levels in place that has a trivial-to-digest visual effect is pretty nifty.
Putting it mathematically, non-linear problems (which are generally harder to solve) may become linear in a higher-dimensional space.