Richard, if you have gluten intolerance or sensitivity, it affects your entire small intestine, not just your ileal pouch. So, "everything" is not really gone, just your troublesome pouch. Not all gluten intolerance is the same as celiac disease, and there are varying degrees (just like lactose intolerance). You may tolerate small amounts and be OK, and that makes you fortunate.
However, if someone has celiac disease, continuing to consume gluten will damage more and more of the small bowel. This can potentially advance to being unable to absorb enough nutrients to survive. In this case, it is not a matter of being able to follow a diet.
They used to think that you could only have celiac disease if you had it from a young age, but they now find you can develop (manifest) the disease later in life.
Jan 