Higher spec LED near the center of the wafer?
Rubbish. Wafers are sliced from a monocrystalline cylinder (called an ingot). The monocrystalline nature of the ingot ensures that the properties are the same on any point of the wafer. Yield is the same for chips from the center as from near the edges.  

The Lenser document Russell links to should trigger some warning lights. First, there's more technical talk than the common customer cares about. Then why tell all this? Well, having someone pay 400 bucks for a flashlight needs some convincing, and some people are sensitive to talk that sounds scientific. The 24 carat gold is also very suspicious. 24 carat gold is much more expensive than 22 carat, yet in this application doesn't really performs better. Why do they mention it? Because it sounds good. And you can't check the claims anyway. Only for the gullible?