Uncomfortable is pretty clear about the purpose of the exercise:

This is from the description of the form intersection homework.

"The purpose of this exercise

This exercise is all about developing your understanding of 3D space and how forms exist within it in relation to each other. It's one thing to be able to draw a form that feels three dimensional on its own, but throwing that form in with a bunch of others within the same space leaves a lot of room for inconsistencies and contradictions to arise. Building up your own grasp and overall belief in the illusion you're producing (something that is pushed that much further by learning how to define the actual positions of forms relative to one another through their intersection lines) helps us push a lot of this work more to our subconscious, where all of the lies we're juggling can be kept in line."

I found this exercise to be very helpful and I regulary practice it.