Well to me its pretty much like the superimposed lines exercise. So its about confidence.

I would suggest just doing everything in this course like it is supposed to be done. Misunderstanding are fine and thats what critiques are for. But if you know its suppose to be done a certain way then id do it exactly like that.

The written part of the challenge does say to go over certain lines a second time to increase the thickness, but in the challenge video Uncomfortable mentions that his lines already have some dynamism due to how he drew them initially (which I take as implying that he doesn't need to add any more line weight because he was able to control the line weight from the beginning), but that for students whose line weights are more uniform, they should increase the line weight a little bit (i.e. with a second stroke). The main goal as I understand it is to provide a visual hierarchy with subtly thicker outer lines, not specifically to draw each outer line twice; though, I can see how it's good practice. I've found I can accomplish this by simply adjusting my pen pressure without having to go over the lines a second time. I also don't see the point of doing 50% more work when we're already drawing and checking 250 boxes, especially when a good affect can be achieved by controlling line weight with pen pressure.