New specialists blur these three roles constantly. Auditors and supervisors do not.
Treatment addresses symptoms and illness through therapy and medication. Case management coordinates and links to resources. Rehabilitation teaches and supports the skills and environmental supports a person needs to function in a chosen role. All three can happen for one person on the same day, but the documentation, goals, and interventions look different.
A useful test: if you did the thing and the participant learned nothing and gained no support, it was probably not rehabilitation. Driving someone to an appointment is transportation. Teaching them the bus route, practicing it together, then fading your presence is rehabilitation.