It is kind of complicated deciphering rules and opinions. However as far as I can see, the 61.75 certificate is a certificate like any other FAA certificate, just with some extra limitations written on it. If you read the rules regarding the FAA certificate, then yes, someone does need a BFR and medical certificate to exercise the privileges and hence, in my opinion, having read the FARs from cover to cover, one must have a BFR and medical for it to be rendered valid.