I accept and understand everything you wrote and I denfinitely know IBS is a physical problem.
Recall Hawkins wrote "Any physical theory is always provisional, in the sense that it is only a hypothesis; you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory." I don't accept your differentiation between theory and hypothesis. However, that issue is off the topic of this board and better left for discussion on elsewhere.
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS