Has a World Baseball Classic game ever ended 10-3?
It has. 10-3 has been a World Baseball Classic final 3 times in 204 games. The first was Canada beat Mexico on March 9, 2013; the latest was Mexico beat Canada on March 15, 2023.
That makes 10-3 the 19th most common final score out of 80 that have ever occurred in World Baseball Classic. One point away, 11-3 has happened never and 10-4 has happened 1 times. Nearly all of its occurrences fall between 2010 and 2039.