Hence the "effectively" qualifier. The physical force of running water is enough to wash off the top layers of microbes but even a small amount of bacteria can

Hence the "effectively" qualifier. The physical force of running water is enough to wash off the top layers of microbes but even a small amount of bacteria can cause food borne illness so no matter what you do there will be a risk. If you dive deeper into the FDA recommendations there are toxicity reasons for not using soap or dish fluid and they actually recommend using a brush to clean firm vegetables and fruits because the abrasive movement is far more effective. I recommend reading the CDC's studies of outbreaks which point out that in many instances the source is cross contamination of bacteria that can't be washed off due to specific molecules that adhere to the surface of produce. The CDC deals with crises and it's in a better position to study food borne illness than the FDA, which provides general advice with nearly a century of history tracing back to the progressive movement in the US. That advice is not necessarily up to date since our treatment of food has evolved to included irradiation, waxing, safety codes, etc. which get the vast majority of microbes to begin with.