Has an AFL game ever ended 15-13?
Exactly once. On June 11, 1898, Sydney beat Melbourne 15-13, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 15-13 in league history.
That makes 15-13 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 16-13 has happened never and 15-14 has happened never.