Not true. While they may indeed eat the contents of their prey items' stomachs, cats are classified as carnivores. Unlike dogs, where you could argue carnivore versus omnivore, cats are obligate carnivores. The link you provided actually discusses why this is, but basically their body lacks the enzymes to completely metabolize plant proteins. In otherwords, they can't digest plants like they can flesh/organs.
I feed my cats a high quality, grain-free canned food. If I had the time to go raw with them, I definitely would. The swich from dry to canned has them much more active, healthy (I had a cat with barfing issues. No longer), and pooping less. I bet they'd do even better on raw.
Raw is awesome, but you have to make sure you meet an animals nutritional requirements if you do that as an only food source. For example, don't feed a chicken breast to a cat for every meal. Obviously, the cat needs all sort of things, including vitamins and minerals, that it wouldn't get from that chicken breast. But there are great sources on the web to help you go raw correctly.
I recommend www.catinfo.org
highly. I think there's info for anyone interested in going raw on there, too.