This argument about super-sensitivity exists IMO largely because other celiacs are afraid of it. What is more frightening than realizing that it's within the realm of possibility to react to the loaf of GFCO certified gluten-free bread in your refrigerator that you thought was safe? Or that there are people with celiac disease who cannot consider eating out... ever? It's much easier to tell the person who is threatening your entire, carefully-constructed, gluten-free world that they must be reacting to fat.
I think it's reasonable to remind people that super-sensitivity seems less common than reactions to other foods and food chemicals, and to remember to consider ALL the ingredients in what they ate. I think it's a jerk move to tell someone they are obsessing. Aren't we questioned enough by family, friends, and doctors?
Afraid of super sensitivity? How is that different than coming very close to death from this disease? That is real fear of which I and many others I have met faced. When I reacted to labeled gluten-free foods, I didn't automatically assume that it was from gluten. There are other ingredients in most gluten-free processed foods. It is always the smart route to investigate all possible sources of a reaction.
As far as being easier to tell a person they may be reacting to fat, maybe it is easier because it's extremely common for Celiacs to have trouble digesting fats, even after recovery. It's called pancreatic insufficiency and it's not a subject heavily discussed. Instead, people become overly focused on one thing...gluten contamination. There are many reasons people react to foods, which should remain the focus when someone becomes symptomatic, which you have been good enough to state in your post.
With regards to obsessing....to be perfectly honest, it happens. I don't regard it as a jerk move to state the obvious.