ch47 - The FODMAP diet eschews grains with gluten as a component (until you rule them in or rule them out), but NOT because of the gluten, which is a protein. The problem with those grains are the oligosaccharides - the "O" in FODMAP - primarily the fructan component, that are the problem in IBS. It just happens that grains with the problematic oligosaccharide sugars also have gluten, not usually problematic in IBS. "Gluten-free" in FODMAP is just a short-cut way of knowing what to eliminate.

From the Monash University website, the developers of the FODMAP diet - https://www.monashfodmap.com/blog/avoiding-wheat-how-strict-on-low-fodmap_10/

The best of luck!