People with celiac disease absolutely react to kamut, spelt, and other ancient grains, and they have plenty of gluten. What he did is interesting but it's obviously not generalizable. I have a friend who is a gluten-intolerant botanist and she even reacts to wild triticae grains she's collected. I haven't read the book to comment further.
The author (which I see is William Davis MD) says "triticum species of today are hundreds, perhaps thousands, of genes apart from the original einkorn wheat that bred naturally." The wheat he used for his "test" was the einkorn wheat grain. He got it from a woman who's the founder of the Heritage Wheat Conservancy (www.growseed.org). I should go look that up, I wonder if anyone can order it or if she just provided it for his personal research. Anyway it apparently is totally different species of wheat and modern wheat comes from a different species. Supposedly you can't even create our modern-day baking feats (think croissants, cakes, bread as we know it) with the stuff, those qualities have been bred into various types of grains.
Just to clarify, the author's point isn't that high levels of gluten are causing issues, but that current-day wheat has been genetically altered to produce pest resilience, fast crop growth etc etc., to the point of causing problems with human consumption. In his opinion, small changes in wheat protein structure spell the difference between "a devastating immune response" vs no response at all. I should have made that clearer given the context of the ongoing discussion here.