A team has finished a game with 12-4 runs on that many hits 1 time since 1897, most recently Cleveland Buckeyes on 4 July 1947. That is about one every 443,004 team-games.
Box score for the most recent one ↗
11-3 11-4 12-0 12-1 12-2 12-3 12-4 13-0 13-1 14-0 14-1 14-2 15-0