You are right of course. The frustration comes because people with adult ADHD have likely had a lifetime of this suggestion, and a lifetime of failing to stick to such modifications, often to the point of developing comorbid issues like low self esteem. When medications finally open the door they have fruitlessly banging their head against, it's frustrating to hear people espousing that, actually, behavior modification is all you really need, even if it is not intended as such (though often it is).