It pointed out that the shoulders were too rounded and the perspective was incorrect for them, making it seem like the arm was just appearing out of the torso. It pulled up images to explain that I wasn't correctly indicating the deltoid's presence. This helped me understand why I felt that the shoulder was hard to distinguish from the torso.

I also asked for help on how to make my posing less stiff and it used the Python script trick to roughly indicate the line of action and how they were very straight and parallel and to reduce stiffness I should have more curves etc.

This wasn't really at the point where I even asked for shading advice.