I think Sarno overcomplicates and casts too many broad strokes.....and his work is a little outdated. I get why....there's a lot of books out there saying the same thing. I don't think it's a bad book but I think it better explains things like Fibromyalgia and Long Covid than back pain.VM why do you think the psych side of the Sarno books are "arguably garbage?"
More importantly, there is evidence that pain education can result in improvement in chronic pain and if Sarno's book piques a persons curiosity in going down that rabbit hole then his book is fine. I've given it to friends who have been sedentary due to LBP and not ready to make any lifestyle changes.
It truly is as simple as...you're not broken....activity to tolerance, increase as able.
Pain is not injury. I have as much or more pain than the next guy but unless I'm sick with a fever...I train.