A physician is incompetent when s/he does not have the basic skills or knowledge to practice medicine. Gross incompetence is a complete and extreme lack of those skills and knowledge.
When incompetence is the issue, you must be completely prepared for the interview part of the process. It is mandatory that you impress the physician at the interview.
It is mandatory that you are able to convince the OPMC physician interviewer that you are in fact knowledgeable and up to date on medical issues in general and that you have an excellent grasp of the specific area of medicine that led to the investigation.
You usually have several weeks between the notification from OPMC and the interview, and you should use that time to refresh your knowledge on the subject.
Remember, you want to end this inquiry at the interview as you do not want to have to prove your competence in a Hearing where you will be asked questions for hours at a time over several days. That is not a situation that anyone would like to go through.