Basically:
Let’s look at the premise behind a catalytic converter. It's job is to assist chemical conversion of poisonous waste gases (CO, hydrocarbons) to more friendly (though still ruining the atmosphere) CO2 and water vapour. The catalyst, as the name implies, does not change in composition, nor will it be consumed, during the process - it is merely there to aid transformation without state change itself. The catalyst needs to reach a certain temperature before it will work properly, hence there is a certain amount of 'flow blockage' that must exist whereby the exhaust flows across the catalyst, for the exhaust gases to heat it up enough - so it's no good to coat the inside of a 3" pipe with catalyst and hope it will work.
Therefore, the stainless mesh, or ceramic, or whatever material you use to flow the exhaust across, will determine the flow capabilities of the catalytic converter - not the catalyst itself. It is my understanding that the stainless mesh is less restrictive than the ceramic monoliths used previously.
What BATMBL is saying, is that MAGIC cats do not have a coating on the mesh. This would mean that the "cat" is little more than a pipe with some steel wool in it.
To be a true catalytic converter, the substrate, be it stainless mesh, or ceramic, needs to have the catalyst bonded to it to work.