I think he means they would disrupt the supply to Britian enough to collapse the economy.

To be truly usefull in the Atlantic the heavy ships would have to be closely coordinated with the submarines and Luftwafe reconissance. That is Raeder, Donetz, and Goering would have to drop their egos and put together a sustained plan to best use the the air, surface, and submarine forces together.

By 'closely coordinated' I dont mean the varios elements operating in physical proximity. Rather their sorties, patrol areas, routes, timing, and attacks are all planned for optimal effect as a whole. This might mean the capitol ships would have to avoid easy combat sometimes, so the submaries could make a better kill. Or a sub skipper might have to make a difficult and unlikely attack to set up a situation for a surface ship many kilometers away. The Luftwaffe would have place a higher priority to reconissance aircraft, and costly air raids on ports an mine dropping missions would need to be done under the Kriegsmarine direction.

If the several pertinant leaders cant get their act together on this the Reich still loses.