Pin distance matters based on layout. If you want a pin up, high flare layout, using a 1 1/2" pin and having to use a P1 hole to get rid of side and top weight because a bowler uses an IT or Switch-grip in the thumb, isn't going to work out so well. You can bottom out the fingers, but then you start to really alter the core shape even more (especially if the core has a weighted puck on top, usually drilling into it decreases diff) plus drilling a bit of weight out of the ball.
Same if you want a pin down layout for control of motion, using a 4" pin distance ball limits you to using P3 or P4 holes, which also increases the diff in most cases and doesn't translate into control.
Pin distance matters.