Excellent point. Often the instructor is so busy introducing new students to particular pieces of the puzzle that the big picture gets neglected*. Books can be an excellent introduction to an overview of the art - history, terminology, concepts, categories of techniques, etc. Many of us learn better when we understand how the topic at hand fits into the context of the art as a whole.It wasn't for the purpose of trying to learn those throws, but when we would learn a new throw in class, I had at least seen it before in some form, and it gave some helpful context.
*(BJJ instructors can be really bad about this. I try not to fall into that trap.)