Dave
as sancap states your medical currency will drop to the ratting that it requires, so if you have a private pilots and you take a check ride, you do not have to have a current medical to pass the check ride. If you pass the check ride and do not have the medical, your rating privileges will drop to the level where your medical status fulfills requirement. In a case that you have a drivers license then you can operate under the privlages guided for a sport pilot, even though you are not a sport pilot to say.
Because the requirements are higher to optain a private pilots, you by default are qualified to operate any of the ratings below the level.
Also, technically you can not fail a bi annual flight review, however if the instructor is not comfortable with your skills then they do not have sign you log book. In this case they will tell you on what you need to work on and you can either do it with them or go to another instructor.
I agree.