that is what I remember from gross anatomy class as well. "infarction of the transverse colon occurs between the distal parts of the vascular beds of the middle colic branches of the superior mesenteric and left colic branches of the inferior mesenteric arteries"
"infarction of the rectum occurs between the distal parts of the vascular beds of the superior rectal branches of the inferior mesenteric artery and the middle rectal branches of the interal iliac artery"
This is directly from road map gross anatomy. His explanation seems to make more sense to me since its at the watershed zones similar to that of the lesser curvature of the stomach being the most common area of ulcers and the watershed area in the brain.