It depends on how you read it, since the short 12-word summary could be read dozens of different ways. There's ways in which trivially, of course, duh, pain is in the brain, where else would it be? But there's also ways in which it stands in stark contrast to what most people implicitly believe.

Take your (you, the reader, not kimmy1 specifically) beliefs about the nature of pain, and explicitly hold it up to the concept of phantom limb syndrome: https://en.wikipedia.org/wiki/Phantom_limb And make extra sure to read the section about mirror box treatment. (That it works at all, for anyone, is the important point, not whether it's a miracle cure for all sufferers.)

You may already have heard about these things, but have you explicitly examined your beliefs about pain to ensure they incorporpate these ideas?

I don't know about fibromyalgia, but it wouldn't shock me that much if there is something a lot like phantom limb syndrome out there that confuses us by causing phantom pain in body parts that exist. For eminently rational reasons it would be a long time before we worked out way down to that hypothesis.