I shouldn't be surprised, Tom, though it doesn't take a rocket scientist to figure this out. One can take a flight review in any category and class of aircraft for which he or she is rated. To be PIC in a given aircraft, you need both a flight review and an appropriate medical. (The key word here is
appropriate. To be PIC in an LSA, the appropriate medical certificate is a driver's license or above.). But, a medical is not necessary to take a flight review, any more than a flight review is necessary to take a medical exam!
Of course,
somebody has to be PIC, so in that 172, if the flight review applicant doesn't have a medical, the CFI must.