A perfect pin axis layout is designed to spin tight and have no flare. When you're using an asymmetric core, the core always wobbles, because it's lopsided/out of balance. Therefore, the pin will never stay perfectly on it's axis and spin tight. When the pin /core is wobbling, it's starts to spin slower, thus losing revs and gyroscopic energy.
This is why symmetrical cores are used for pin axis. When you nail the drilling, the pin never wobbles going down the lane, spinning perfectly tight and fast, like a spiral thrown football. This stores up the most energy, because the ball is spinning faster.
But, because of no flare, the ball needs more dry boards down the lane to react. When it's right, it's really right..!! =:^D