A lot of our legal foods contain di- and poly- saccharides. Squash and nuts, for example, contain starches. But there are some things which have been shown to be tolerated; and other things which are sometimes legal and sometimes not. Pectin, for example, which is present in foods like apples but not okay to consume in concentrated forms.
I understand your confusion, but if you try to analyze everything you will only make yourself crazy. The SCD, as someone once put it, is "evidence-based." It's been shown to work as it is. If you find you have trouble with a legal food, you may just have an individual sensitivity or you're just not ready for it. That's not at all uncommon.From the LI listserve
Through the (SCD) Specific Carbohydrate Diet, explained in this book, our son was able to get off medication and thrive. He healed himself and was able to go away to college. Last month he had a relapse, had surgery and by going back on the diet he was able to put himself in remission. The doctors are amazed with his latest tests and told him he did not need medication, but he must stick to the diet. I have bought over a dozen of these books and shared them with doctors, family members, and friends. I strongly recommend this book for any IBD/IBS issues.