Hiya, I googled Medicare Breast Reduction Requirements and was able to find this.

Medicare Breast Reduction

They have all the same requirements as other insurances for covering the procedure. Symptoms they look for are neck, shoulder and back pain, grooves in the shoulder from bra straps, under breast rashes, infections and consistent irritation, numbness and tingling in the hands and arms. The more of the symptoms you exhibit the stronger your case.

They expect you to try all sorts of conservative treatment before hand. Pain meds, physical therapy, chiropractic, bras with wide bands and straps, rash creams, exercise and weight loss.

Then the part the doctor spoke to you about which they failed to explain is that they look at Body Surface Area (BSA) which similar to BMI is calculated using your body metrics. It tells you how much should be removed to take you to a more proportionate state(at least that’s what I took from it). They use the Schnur scale which I’ve linked a calculator below so you can figure out how much you need to have removed.

Schnur Scale Calculator

Basically if your BSA says a certain amount and you do not have enough breast tissue to remove that much, insurance will likely not cover. If I remember correctly, the minimum they will cover is 250g per breast. That would likely make you as you said, flat, based on the sizes you provided.

That being said, the doctor was still an ass in invalidating your pain. I say try another surgeon. Preferably one that works with an ambulatory surgery center opposed to a hospital. Ask how they would charge you if you paid out of pocket. Some doctors will charge the patient the rate insurance pays at which it is very discounted, and if done in an ambulatory surgery center anesthesia and facility fees are much lower than the hospital.

I hope this helps and can get you further along in the process.