The official word to BGO's is application has to be complete before USNA submits a candidate to DODMERB. This is a change from the past, which was a little less official but typically triggered at around the 50% mark,
That said, USNA can submit a Candidate's name to DODMERB whenever they want ..its a balancing act of not submitting names and commencing the process until it looks like the Candidate is going to go through with the application (keep in mind, somebody has to pay for all these medical exams, and there is not sense paying when the candidate isn't going to follow through) and getting the Medical qualifications done in a timely manner. The balancing act is a continuing struggle, but really a non-issue from the Candidate side . Bottom line, the timing of medical is within your control -- get the application done in a timely manner if you want to avoid delays in getting medical done.