Lol that is not true at all.
Have you performed a spectrum analysis of your microwave recently?
You don't have to. You just have to do this: Faraday jails partially/completelly block an electromagnetic source if they are connected to ground. As you don't believe in no component of the microwave, do this:
-Take a copper cable, connect it to the external case (specially the door) and on the other side to a tap.You've just made a Faraday jail.
-Take a cup of water, with nothing more than cup, and water. Hold it next to the door. Put a cup of water (this time be sure to PUT SOMETHING like tea on it, itīs really important, the water could explode in your hand) INSIDE of the microwave and switch it on. Check both water cups.
What happens? The microwaves used on your "Gamma wave oven" belong to the short wave radio zone of the electromagnetic spectrum. That means that a Faraday jail can stop them (If you don't believe me, wrap a radio with several layers of tinfoil, you should stop hearing anything if the antenna is not touching the tinfoil). But what about gamma rays? They can pass through almost every material in the world. I think you donīt need nothing more to understand my point. Oh! And try to call to a cellular that is inside a switched off microwave.