The D4 Medical is like an MOT, it is just a snapshot of the vehicle, or person on the day, the brakes could fail tomorrow or the driver could have a stroke.
I know my own doctor would fail me if I went for a medical tomorrow, but a doctor who doesn’t know my medical history would probably let me pass. My father died on the 21st October 1977 whilst taking his driving test, this was only a couple of months after having a medical. He was 50