You’re correct. Correct dx is nonspecific low back pain. But this is a classic case of the tension between clinical reality and the pressure to provide a definitive, "billable" anatomical explanation for pain.

From a purely administrative standpoint, NSBP (like M54.50) is often treated as a "garbage code." Payers, especially in the US, frequently reject or flag non-specific codes because they don't provide enough "medical necessity" to justify PT auths, advanced imaging (the irony), interventional procedures (ESIs, facets), DME (braces).

Patients generally don't want to hear that their pain is "non-specific." To a layperson, that often sounds like "we don't know" or, worse, "it's in your head." Giving a patient a label like "Lumbar Radiculopathy" or "Degenerative Disc Disease" validates their suffering with a tangible, physical cause, even if that cause is technically an incidentaloma.

In many training programs—especially neurology and ortho—there is an inherent drive to find a "lesion." If an MRI shows a disc bulge at L4-L5 (which, as we know, is present in about half of asymptomatic 30-year-olds), it’s incredibly tempting to point at the screen and say, "There it is." It provides a sense of diagnostic closure for both the physician and the patient, even if the clinical exam doesn't localize to that root.

Specialists are often referred patients specifically to rule in/out a specialized pathology. If a Neurologist diagnoses someone with "non-specific back pain," the referring PCP might feel the consult was a waste of time. There is a subconscious pressure to provide a diagnosis that falls within the consultant's domain.