/ic/ - Artwork/Critique

I'm doing the drawabox stuff and got a question about the rotated boxes that I feel the guy didn't make clear enough.

I understand that as a box moves e.g. right in the image, the VP that used to be in the exact middle (for the center box) moves to the left, and the other VP from the side moves closer to the center. Same thing, but vertically, when you move to a box that's above a previous one.

So I'm assuming the VPs for the red box in the attached pic would be as I've written there? Since the red box hasn't moved horizontally compared to the box underneath it, the VPs on the left and right haven't moved horizontally either, but since the box has moved vertically, those VPs have still moved along the Y-axis. Same thing compared with the box next to it, but moving on the other axis. And that's why the third VP (which was in the very center for the center box), has moved on both axes when compared to the center box. Correct?

I know the whole exercise is about estimating and getting a feel for space, but the guy only explains that you can approximately guess based on the neighboring boxes' edges, which doesn't really help understand what exactly is happening at all.