Alright, since those are especific questions, I will give you the epecific reasons why the bean works that way. At the very end are the direct answers and critiques, the rest is the explanation and hopefully it's clear enough (was difficult to me to condense it). Full Explanation: You have to remenber 2 key parts about this excercise: 1.- The whole point of this exsercise it's to exaggerate, the streching, pinches and twisting are going to be even clearer in the bean than the pose itself, 2.-The bean is meant to be an analogy of the torso, and doesn't have to represent the exact anatomical information, but to represent the motion. For example: the first pose shows a curve created by the back of the rib cage transitioning to the neck trough the trapezius. You can analyze the entire line and use it to your advantage in a more difined gesture drawing, but when studying the bean you should ignore it, because the bean does not include the neck, it's just the masses created by the ribcage and pelvis+middle fleshy part. Visualize your first form as the rib cage, imagine the oval representing ONLY the rib cage (no muscles) and think how the center line travels in this simple oval. For the second pose is the same, the center line doesn't have to represent the exact line that the spine creates. Unless the model is a contortionist, you won't see a clean pinch in the back; but since the bean it's an exaggerated analogy, you should represent the pinch in the back if the model it's bending backwards. Short answers: 1. He IS ignoring the neck and only considerates the rib cage. 2. Another way to represent that pose with the bean is with a pinch in the back. Regarding the critiques, keep in mind the 2 key points. The center line must flow within the volumes you draw, not necessarily the exact line you see. For things like understanding the forms or the lines dexterity, it's pretty much practice. Remember that, regardless the tool or medium you use, draw from your shoulder. Hope this can be useful to you.