As detailed in the video above (See from 02:50), if the deep core/abdominal pressure is weak, the rib cage goes down and this naturally brings the neck and shoulders down and forward.

As shoulders roll in with elbows bent, the biceps muscles naturally sit in a shortened position. Then, it is easy to get tight (Yellow arrows) and tight muscles pull its tendon away from the bone (Purple arrow), which increases tension. This increased tension can cause friction between the tendon and bone, resulting in tendon problems. Therefore, this program not only focuses on restoring the function of the biceps tendon but also correcting any postural imbalance like rounded shoulders.