I dont think they are overdiagnosed but there is a large number where the outcome shouldn't mean benefit. It should mean people explore coping strategies, and try to improve things themselves and put on a belt and braces.
However there are then also a large number that need support and its just not there. So, guess what, things get worse!
I fear he is lumping almost all into the first category when it's simply not the case. Some do, but my no means the majority.