I think you are confusing the information on the hammer nutrition website. What it's basically saying is, if you head out on a ride and have elevated blood sugars (i.e you have eaten within 3 hours) then your body will release a higher percentage of muscle glycogen to fat as you ride, thus making your endurance lower. If you start out on empty, or 3 hours after eating - then your blood sugars will have returned to normal, your body will start using a higher percentage of fat and you will have better endurance. This theory certainly does work - I use it myself in longer races. However, your performance will be better if you eat before - it's just that you won't have quite as good endurance. This has nothing to do with blood divertion to the stomach - that's an entirely individual thing.

For me, I don't cycle well with a lot of food on my stomach. I tend to stick to some cereal or toast/bagel and coffee an hour before, I know some of my cycling buddies seem to be able to perform fine after eating a lot more. Just find what works for you. I personally feel that what you eat the night before is most important.