In the clinical world, it is well recognized that neck pain often improves when the next adjacent spinal region (the thoracic spine) is treated. There are numerous theories as to why this change is seen ranging from the very mechanical (if your mid-back is stiff, your neck endures more stress) to the more modern, neurophysiological explanations.
https://skullate..com.ng/2018/01/thoracic-mobilization.html?m=0