I am going to really mess you up LOL.
I have different bowlers use different starting points because everyone has a different shape to their armswing. I try to use an armswing that is most natural to the player that will still put the ball on the path I want.
Another reason to change the starting position is bowlers often push one way or the other without knowing it. They "think" they are pushing straight ahead but they are not. Then again because everyone don't have the same flexibility in the shoulder I sometimes have to ask the bowler to hold or push the ball in a different place than would seem correct.
I am sure that every coach has a place where he starts bowlers out, I do too.
But more often than not I end up changing it a little for each bowler.
Now to really blow your mind
The best starting position-stance-pushaway-armswing..... for you today may not be the same for you in 6 months.
Bowlers,balls,lane oils and patterns all change over time.
It can be very hard for a bowler to keep up with all these changes on his or her own. That's what makes a good coach worth his weight in gold.
Bowl great!
Ron Clifton