This is a systemic review. A RCT would absolutely find a difference. The whole point of this satire is to point out that there's not always studies on what you want to know. "No randomised controlled trials of parachute use have been undertaken"

Flossing has absolutely been studied. Professional flossing seems effective at combating gum disease. Telling people to floss doesn't seem to be. It's unclear why (is it just compliance effects? are people educated on how to floss still ineffective? etc.)