So there are a couple corrections I should note to what you've mentioned. Most notably, form shading isn't something we worry about in this course. In this section I do talk about how texture itself can serve as a way to convey form shading, but as noted in the title of the section, form shading isn't something we want students concerning themselves with for our purposes here. When drawing your textures, try to focus on cast shadows only.

The texture section is easily the one that is most needing an update, although our slow-and-steady overhaul process has only just reached Lesson 2 (most of our resources are committed to providing official critique and managing the community as a whole, so it is very slow), and a lot of the confusion arises from the fact that the demonstrations are very old - especially for the dissections. I believe that video is from 2017, which was before we realized that it was much more effective to have students focus on implicit markmaking and cast shadows.

Prior to that point, when it came to textures I was still trying to largely regurgitate what I was taught in my Dynamic Sketching class with Peter Han, which still involved a lot more "feeling things out" rather than explicit rules - so while when tackling this in the overhaul I probably will move away from reflections (which are not the same as texture), they're there currently because "texture" at the time was less about implicit markmaking, and more just about decoration.

We have updated the text portion of the material, as well as the texture analysis stuff to better focus on implicit markmaking, but the dissection stuff being more outdated has definitely led to uncertainty amongst students. The way we'll be moving forward though will tie in better to the overall focus of the course, bringing it all back around to developing those core 3D spatial reasoning skills. A cast shadow is itself something that helps to define the relationship between different structures as they exist in space - the design of the shadow shape itself establishes how the form casting the shadow relates to the surface receiving it. That's why, despite being superficially very different from all the construction we do here, it actually falls right in line with everything else we study in this course.

Despite the understandable confusion, it's best not to worry about it too much. While mostly we haven't updated it yet because we wanted to work through the course in order from start to finish, the fact that these issues/confusion are a lot less of a problem for those students who just push through and do their best has also reduced it as a priority. Even once the material's updated, the expectation won't be that you'll "get it" where it's introduced. It'll continue to be one of the parts of the course that throws you into the "deep end of the pool", to plant a seed in your mind as to how you can start thinking about these concepts, so that as we continue to work through the remainder of the course, exploring those 3D spatial skills in different ways, that it will all come together into a well-rounded understanding of 3D space.