The CORE size would not necessarily alter the size of the ball. They would just wrap it tighter. As long as the weight and outer size are within specs, no one would know. There was a report on TV where the balls being made in Central America were being wound too tight.
As far as size, the American League has a slightly smaller specification than the National League ball, or at least they did years ago.
I think I've found the cause of "moonbatism".....