FODMAP is real, most of the people I know who are on the diet where it has helped have SIBO (small intestinal bacterial overgrowth). The problem is that SIBO can have a bunch of causes. Mostly what I hear is that they get the antibiotic and whatever underlying cause can't be found or fixed so they get put on a low-FODMAP diet to stop the bacteria from growing out of control. Doesn't work for everybody, guess it depends on your gut bacteria and what they can survive on, but it seems to work for enough people that doctors recommend it.