Carbs work on the same principle. Lets say a carb is rated at 700 CFM. We stick it on a high performance 350. We do tests and find the engine only wants 585. The engine runs perfect and has great power, but since the engine only demands 585 should we swap the carb for a smaller one? not really, why is because a carb will only feed a engine what it demands.
Some believe because it`s flow rate is 700 means at wide open throttle it`s flowing 700 like it or not and that`s not the case. If the engine can`t pull it in then it`s not being used. In the real world, Engine demand figures and carb sizes are out to lunch. Even during the horsepower wars of the 50`s and 60`s a 283 with power pack heads that had puny 1.71 valves but yet had a good sized cam, high compression and other goodies came with two four barrels, what was the chance of a 283 using that much CFM? not much.