It's widely known that a bread crumb will have harmful effects if you have celiac disease. A human who has a peanut allergy will have very negative effects from eating a fraction of a peanut.
It's also widely known that foods that are fine for one species can have toxic effects in others. A well-known example is that chocolate is fine for humans (in moderation) but deadly to dogs in similar quantities.
A finding that humans without an allergy or hypersensitivity to it react to wheat gluten with brain inflammation would be big news, as would a finding that a large fraction of the human population has a hypersensitivity.
Not sure how this is common sense. If it were mice engineered to have celiac disease or recently diagnosed humans, it might make sense. Extrapolating it to the general population of a different species in a part of the body not related to digestion is a bit of a leap.
(emphasis mine)
I don't follow how this is common sense. It looks like extrapolating from your condition (celiac) and projecting it onto those that don't have your condition (non-celiacs).