Exactly! I have a friend with a severe allergy to corn. A few years ago he visited with an old friend in Maine who has been growing heirloom corn for years, and he could that corn with zero problems.
I was diagnosed with a serious gluten sensitivity at the age of 50. Even though I cut out foods with wheat, I kept having issues. After some trial and error, I realized I couldn't tolerate oats either (even certified gluten free oats). My gut reacts to oats as if I'd eaten gluten. Same with buckwheat and a few other grains. And most bizarre of all, coffee...
Agree with another poster that science just hasn't caught up yet.
I was diagnosed with gluten sensitivity in 2013. That first year I was diligently avoiding wheat like the plague but still having issues. By process of elimination, I realized oats effected me the same way that wheat gluten does, and can't eat it anymore. Two years, still having issues...