This is not mindfulness. They actually compared against a mindfulness-based treatment (MBSR) and found their method performed significantly better.
Looking at their patient groups on Table 1, it seems MBSR and Usual Care had participants with more spinal injections and surgical interventions. MBSR and Usual Care have higher "Pain bothersomeness" scores and "Roland Disability Questionnaire Scores" at the start.
It's a very small-scale pilot study. I am very skeptical it's not a ploy to try to sell his books.
So - I wouldn't be in any way surprised if there are other related treatments which have high levels of efficacy...
[1] https://en.wikipedia.org/wiki/Mindfulness-based_stress_reduc...