Ssssorry? Just kidding. I had to do speech therapy when I was younger for my S's. I guess it didn't work as well as I thought.

Good point! You are absolutely right. Value can create the illusion of form on a two dimensional surface. I like to keep form out of the loop somewhat when talking about 2D art though, because people have become very accustomed to using the word form when they actually mean shape. I like to draw a definitive line between the two for my beginning students. That said, we then talk about how to create the illusion of form using value and other techniques such as atmospheric perspective, linear perspective, positioning, size, clarity, etc.

Good point. Further analysis is always great, but this video is an introduction to the art elements, and aims more to help students be able to recognize how they are used in different artworks.