There is a significant distinction between celiac disease and the broader categories of gluten intolerance and other food intolerances. These are all immune-mediated disorders and tend to be hard to diagnose and tricky to manage because they often have a now you see it, now you don't character.
In celiac disease, a toxic and immunological reaction to gluten damages the lining of the small intestine and results in the malabsorption of nutrients and development of other ailments based on the combination of nutritional deficiency and immunological reactions. If one stops eating wheat, rye, and barley and foods and beverages containing them early enough, the small intestine almost always heals, nutritional status improves, and secondary ailments diminish or disappear.
If a recovering celiac patient then starts again eating foods with gluten, things may seem fine for a while, with a sense of exhilaration as one feels free of the burden of constant dietary vigilance. Nevertheless, the small intestine and the body itself are gradually deteriorating as the inability to process gluten takes its toll. Bluntly put, there is no known basis for recovery from celiac disease except lifelong avoidance of gluten.
There is also a new and evolving category of non-celiac gluten intolerance in which it seems some patients may resume eating gluten after a period of avoidance. Perhaps the author had that instead of celiac disease. Or it may be that other factors were involved, such as the higher gluten fraction in newer wheat varieties that tend to be grown in the US, or maybe the author is more tolerant of the yeast varieties used by bakeries in Europe.
In sum, the author seems not to have a clear understanding of his own health issues and is an unreliable guide for anyone else.
Yes I get the sense author was not celiac (rather rare) but ‘gluten intolerant’ (a sort of trend) ...