Why YSK this is that some of the soap absorbs into the fruit, especially berries, and let’s say you are washing your cherries with dish soap, and you eat them. That story ends with a long bathroom trip as soap makes you a little queasy. ETA: Nobody has heard about this?! I see it in the southeast where I live.
You can wash it with vinegar though. Washing your berries with vinegar as soon as you bring them home will dramatically improve their shelf life.