Every case is unique, and nobody is perfect and knows everything. To me, both authors are not trained well scientifically. However, they all came with a solution to solve their problems and live a better life.
We are all ordinary people here. What we can learn from other is the spirit to change when they struggle in real life. There is no method to fit all, unfortunately. We should appreciate these who have the courage to share their experience even we may disagree with their method.