Exactly. It teaches you how to draw. An orange is just an orange to me unless I'm drawing it. Then it becomes an orange I have to focus on while I draw.
What the book is really teaches you is to not see an "orange" at all. The process is pre-verbal. By the time you see "an orange", the information you need to produce an effective drawing of it has already been condensed down into a verbal token and your attempts to draw it fail because you're drawing the visual archetype stored in your brain instead of the specific spatial pattern of hue and value that is in front of you. The exercises in the book are intended to help you gain access to your visual processing pipeline at a lower level before object recognition has been applied.