A 71-year-old woman with limited cutaneous systemic sclerosis (anti-centromere antibody positive) and CREST features presents with recurrent iron-deficiency anemia (Hb 6.8 g/dL, ferritin 6 ng/mL) requiring transfusions over 18 months. Upper GI endoscopy reveals multiple longitudinal red vascular stripes on antral rugae radiating centripetally toward the pylorus, creating a classic "watermelon stomach" appearance. The stripes **converging on the pylorus (marked B)** are composed of dilated, tortuous mucosal capillaries with fibrin thrombi. Which of the following best explains why the pattern of vascular ectasia in this patient is ANTRUM-SPECIFIC and CONVERGES TOWARD THE PYLORUS rather than involving the fundus and corpus?