I don't think they are in any way minimizing ADHD. ADHD is diagnosed by symptoms, and has a large number of different possible underlying causes, most of which are not well understood. When ADHD is caused or worsened by an allergy, that in no way makes it not real ADHD, but can make it easier to treat, if the allergy is identified!
It's known that ADHD is highly heritable and has some specific genetic mutations weakly associated with it, but it can also be caused by traumatic brain injury, toxin exposure, some food dyes and preservatives, and allergies. It's very likely that many of the heritable genetic factors themselves have interactions with external environmental factors, and can therefore be treated with environmental manipulation, if we can understand it better.
It's known that ADHD is highly heritable and has some specific genetic mutations weakly associated with it, but it can also be caused by traumatic brain injury, toxin exposure, some food dyes and preservatives, and allergies. It's very likely that many of the heritable genetic factors themselves have interactions with external environmental factors, and can therefore be treated with environmental manipulation, if we can understand it better.