I'm inclined to believe that preventing food particles from rotting between my teeth is a measurable impact in itself, regardless of whether it directly impacts my health.
Your assumption is that the floss is removing something that brushing does not. Ask your dentist why you should floss and the answer is not removing occasional lodged pieces of food from between your teeth, but cleaning under the gum line. There is no evidence to suggest it works that way, this is what the long term studies have determined.
So by that rationale, after a thorough brush, flossing would never remove anything?