My "shoulder angle" changes all the time with my position -- it can be ~90 degrees when I'm dodging a headwind in the drops, but it's often not. "Shoulder angle" sounds like one of those BS metrics like KOPS that came from observing a lot of bike riders, not from anything logical.

The picture shows someone who is sitting upright on the saddle, bending their back rather than rotating their hips to lean forward. Once that's fixed, some more "shoulder angle" should magically appear.