I have a hard time buying that too. I guess if you have been suffering all sorts of symptoms, and then get rid of the gluten symptoms you could have the symptoms from your other food intolerances remaining. But, why would you all of a sudden have much more severe symptoms to another food when you eliminate gluten? Why would you be able to eat that food when you grow it yourself, but not when you get it from the grocery store? That makes no sense to me. In my mind it makes cross contamination the more likely culprit.
Steph, I don't know WHY, but it happened to me. I had mild digestive symptoms and bad psoriasis. When I first went gluten-free, all I ate was whole foods - meat, potatoes, veggies and fruit. My gut symptoms were gone and the psoriasis almost completely healed after YEARS of having it. Then after a few weeks I made some gluten-free cornbread and BAM!! Sick, and the worst psoriasis flare I had ever had. I couldn't even walk! Couldn't pick anything up because just bending my fingers was excruciating. I ditched the corn and it healed again. Now if I get any corn by accident I get sicker than I do with gluten.
Before going gluten-free I ate corn several times a week. My psoriasis never flared as badly as it did after going gluten-free. I have no idea why, but at this point it doesn't matter. I just know I'll never eat corn again. Maybe at some point I could get it back, but I'm not even interested in trying it. It limits me so much, but that limit is good, because it keeps me off processed foods. I've never eaten such a healthy diet in my life. If all of a sudden they found a cure for celiac and corn intolerance, I'd STILL keep eating the way I am now.