Has an AFL game ever ended 56-28?
Exactly once. On June 22, 1968, Carlton beat St Kilda 56-28, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 56-28 in league history.
That makes 56-28 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 57-28 has happened never and 56-29 has happened 3 times.