First of all, if that is what they are telling you, you may have grounds for a congressional complaint (or at least an IG complaint) that they are using illegal tatics to prevent service members from seeking medical care for valid medical conditions. I acknowledge the fact that the Navy has the right to medically discharge an individual with this condition: However, there are protections in place to protect servicemembers within two years of retirement (check with your base legal office). Secondly, if you have already filed your retirement papers and the Navy has excepted your request to retire, for them to say they would withdraw that approval and medically discharge you is most likely an illegal act. You may want to seek legal advice.
Your next option is a path what I feel would be the path of least resistance (where you can get both your retirement and your dissability without fighting the system). Now, you should verify what I am going to suggest ASAP with your VA Representative (before you take any action and especially before your official retirement date). If I remember correctly, you can file for your dissability with the VA up to 1 year after your official retirement date. What does this mean to you? It means that if you are diagnosed with sleep apnea and subsequently issued a CPAP within 1 year after retirement, you can include this in your application for dissability after you retire. Remember, you must not file for your dissability rating before you have been diagnosed with sleep apnea. The next important thing you must remember, you MUST file within 1 year (365 days) after your official retirement date. If you delay in filing beyond the 1st anniversary of your official retirement date, you will forfeit any possible consideration for dissability. Once approved for the dissability rating, your dissability payments will be back dated to your 1st retirement check.
I would also like to let you know that I thing the tatic they are trying to use on you is bullsh*t. First of all, sleep apnea is a serious conditions which affects your cardiovascular health. If you require a CPAP, the use of CPAP has been estimated to extend you life expectancy approximately 4 years. This is not to mention the quality of life between now and then. Shame on the Navy to try to take this approach to save a few $. Secondly, if they feel that too many people are getting sleep studies, we need to remind them that it takes a physician (who has actually examined you) to give you the referral for the study. If your symptons did not warrant the study, you wouldn't have gotten the referral in the 1st place.
Don't forget to make and keep a copy of your medical records before you retire. After you retire, your official medical records are sent to a repository and may take months to retrieve any information from them (that's if they are not lost between the time you retire and you need them).
Last of all, I am not a lawyer or qualified to provide you legal advice considering your retirement and dissability. Please verify the accuracy of my statements from official sources before you act.
Keep us informed on your progress.