That's an EXcellent point about cats eating the gut! They would get lots of fat that way too. Naturalist Farley Mowat who wrote "Never Cry Wolf" which was made into a movie ate nothing but mice to prove that wolves could live off mice. He started out by gutting the mice but got cravings for fat, so kept the guts in his diet. Poor man! But he found he could live just fine off nothing but wild mice!
I always thought that show phrased it a bit extreme since cats will eat grass and they know best. I think when they are low in certain minerals they go for veggies. I had a cat that loved canteloupe seeds. :)