Will improving the ability to detect emotions improve clinical outcomes? We don't know, but their initial evidence looks promising: take a look at the JAMA Pediatrics paper (https://jamanetwork.com/journals/jamapediatrics/fullarticle/...) and the Nature Digital Medicine paper (https://www.nature.com/articles/s41746-018-0035-3), which are both linked to in the article:
Would a therapy like the one you described be better than a technology like this? Maybe. But therapy also very expensive, time consuming, and prohibitive for people who don't have time to take their kid to it every week. We are always looking for new approaches. Even if technology like this doesn't work out, learning why it doesn't work will be helpful for developing future treatments which are better. Remember that this is active research, not an established methodology. (Don't be put off by the "breakthrough therapy" designation mentioned in the article, which is a bureaucratic technical term used by the FDA.)
The paper you linked to is about monitoring, and is not useful by itself without a therapist to interpret it and evaluate it. There is not yet established methodology on how to use this kind of data.
On a related note, there has been a lot of interest recently in real-time feedback for enhanced therapy and treatment. There is a growing literature on neurofeedback in particular, such as reducing depression symptoms by training someone to control their neural activity (e.g. see https://www.youtube.com/watch?v=Xb7bgNo3sUs). Exciting stuff!