That is the $20,000 question.
First, if adults are now taking ADD meds, it can be because there is a real population of the needy who were not diagnosed or medicated. Is that over-prescribing? Well, only if we can find that the people taking it are not fitting the diagnosis of ADD.
That is a valid question, but as the article points out, this report does not really nor can it, really answer that question. So, instead, we tend to look at the question and answer it based on our own ideas. If you think ADD is not a real or wide-spread problem, then, yes, it is over-prescribed. If you think meds are a valid part of treating problematic problems, then this is progress. If you think that perhaps people exhibit ADD symptoms due to their context, such as more stimulus, too little exercise, too little positive work structure, too many boring jobs, and so on, then we can medicate people to help them conform to context, but we are avoiding a full-spectrum approach.
I tend to be in the latter two camps. Meds can help. But it is worth asking if we have the best contexts for learning (kids) or working (bigger kids) for ADD people to be productive and resilient.