Not an idiot. CAB comes from Angus cattle. Angus cattle is noted for its high backfat contents (do the math). Just think where angus comes from? England. Think of the climate of England? Damp and cold (usually rainy).... In this climate, Angus cattle depends on their bodyfats to survive because of their low hair ratio. Look at Highland cattle; they do not depend on bodyfat because of their excess hair counts therefore Highlands are noted as a lean beef breed (whether grain fed or grass fed). Shorthorns and Herefords have more hair per square inch than Angus... I think Angus, of all English breeds, have the lowest hair per square inch.
Overall, Angus (CAB) beef is fatty beef. That is why Angus got a third category!