I suspect what's happening with all the people who this works for is that given there are some people who have a psychological component to their pain and some who have a mostly physical component.
Even if there are far fewer suffering from the psychological version, they are the ones who physical treatment will fail for. So they will be the ones that get as far as trying the pseudosciencey approach to dealing with the pain. So the mind body approach will have a high success rate amongst the people trying it even if it would be a terrible initial remedy to try.
Even if there are far fewer suffering from the psychological version, they are the ones who physical treatment will fail for. So they will be the ones that get as far as trying the pseudosciencey approach to dealing with the pain. So the mind body approach will have a high success rate amongst the people trying it even if it would be a terrible initial remedy to try.