Has an AFL game ever ended 28-13?
Exactly once. On September 9, 1899, Sydney beat Essendon 28-13, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 28-13 in league history.
That makes 28-13 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 29-13 has happened never and 28-14 has happened never.