I'd think this is coming out of the "cross reactive" panel that one of the labs is doing.
AFAIK, some people (not all) who are sensitive to gluten have the same kind of reaction to coffee. Now that kind of cross-reactivity can occur because the general configuration of some molecule in a food (or its broken down products) is sort of like that in another. As I understand it, that's NOT likely what's going on with coffee. What's probably going on there is that people so commonly drink coffee with pastries, that the body goes on red alert when it detects coffee entering the system.
You remember that thing "If it's Tuesday this must be Belgium?"
Something similar. The body is thinking: "If this is coffee, there must be a Danish pastry coming soon."