Has a World Baseball Classic game ever ended 10-9?
Exactly once. On March 9, 2017, Italy beat Mexico 10-9, and no World Baseball Classic game before or since has ended that way. When it happened it was a scorigami, the first 10-9 in league history.
That makes 10-9 the 47th most common final score out of 80 that have ever occurred in World Baseball Classic. One point away, 11-9 has happened 1 times and 10-10 has happened never.