That is not true for the air force. It is in the regulation that a person who is being medically retired should get a retirement ceromony just if you did your 20 years. So I would think the same holds true for the Marines.
Just if... or just
as if?
From the way I read the Army Regulations if you are being retired you are due a retirement ceremony, PERIOD. There is no distinction between someone who made 20 years and someone who is being medically retired because they are disabled due to their service.
IMHO, the Solider, Sailor, Airmen, or Marine who is forced to leave the service early due to being disabled by that service IS DUE a retirement ceremony. Spending 20 years or more in the service is a sacrifice of time spent for your country, and should be recognized. But so should the SM who will deal with their service connected disability for the rest of their life, that in my eyes is the higher sacrifice in service of your country.
Short answer, hell yes you are due a retirement ceremony.
On that note, I asked for a retirement ceremony from my Army National Guard unit due to being medically retired with a severe spinal cord injury. The readiness NCO told me flat out they wouldn't spend any unit funds on a plaque or anything, and given his attitude I doubt I'll be receiving a Army Commendation medal or Meritorious Service Medal as is customary for a retiring Soldier.
I retire in 6 days, and the Unit Commander told me 3 days ago that the earliest they can do a retirement ceremony is August. He was good enough to say that I did deserve one, but as I lay here after 3 hours sleep before the pain woke me up again, I can't help but feel that it's more a formality than a sincere act of appreciation for the sacrifices I have made and will continue to endure.
I am still determined to have the ceremony, if for no other reason than the fact that injured or wounded Soldiers should not be brushed under the rug and forgotten.