The question you pose would be best reserved for a physician. If you disagree with his assessment I would definitely consider requesting an IME and speak to a local work comp attorney to assist you through the process.
You probably would need to consult an Attorney to break the report down for you. Range of Motion loss is a rateable disability, but whether other factors are present to justify particular category classification often requires legal analysis of the entire medical report.
We offer general concepts, but you should give ALL your facts to a licensed Attorney in your state before you RELY upon any legal advice.
MMI and the AMA Guides are terms specific to workers' compensation claims. When dealing with shoulder claims, the primary measurement of recovery in the AMA Guides is how much range of motion you have. Tennessee law requires that assessments of work injury impairments be done using the AMA Guides, which is a book put out by the American Medical Assocation. The criteria used for shoulders has to do with measuring the different ways your shoulder can move (up, down, side, etc.) and to see how much of that you can do on your own. It is simply a guide for doctors to use to determine how much you are physically limited. The use of "massive" sounds like that doctor's way of trying to get you to where you have "massive" range of motion in your shoulder. You can keep in mind - do you have normal ability to move your shoulder? If not, you probably have not achieved "massive" results.