"3.2 In the event that a player pockets both their own game winning ball, and their opponent’s game winning ball, both on the same legal stroke, then the shooting player wins. There are no ‘ties’, and it does not matter which ball drops first, as long as they both drop as a result of the same stroke."
Since it is impossible for 3.2 to come up in any tournament where there is no spot, it would be wise for players to agree before a match to follow this rule if there is a spot.