I think you could have phrased this differently but there is something there. Depression is a complex and multi-faceted challenge that can have many underlying causes and is subject to a number of psychological forces. The author takes the approach of managing the superficial symptoms whereby depression makes people non-functional, but there are probably underlying causes that will reemerge in various ways down the line. Managing only the loss of productivity without addressing underlying concerns has a high likelihood of just masking the problem. They might find themselves a year or two down the line with some accomplishments but still nagging feelings of self doubt and failure.
I'd recommend "Feeling Good", a book by David M. Burns (site here: http://feelinggood.com/)
It's amazing how some very productive people lead inner lives of desperation and pain due to bad self-talk and reinforcement of negative feelings.