Are those contradictory positions? For example, consider lactose intolerance. It is true that a change in diet can "cure" lactose intolerance (in the sense of you never experience any symptoms), but lactose intolerance is still physiological.
Similarly, is there any research that mindfulness actually cures ADD, rather than acts as a coping mechanism to reduce the symptoms of ADD.
At the moment, there's no way to measure whether someone is cured. It may even be that "curing" ADD has some unintended/negative consequences -- perhaps some people have good qualities that are linked to their ADD. I really don't know.