Rick, tell us about the men's game in this respect please.
With the rise in popularity of the ISC (International Softball Congress) in the mens elite level came the pitching rule that allowed the pitcher to start with only one foot on the rubber. The Kiwi's mastered this faster than the rest and became dominant in the sport.
When you watch an elite level mens pitcher they start with their landing foot significantly behind the rubber to the point that they get a running start off the rubber. They generate tremendous levels of energy and then when they land they transfer it into the hip snap, shoulder, arm, and finally to the fingers.
Almost all the dominant pitchers in elite level mens fastpitch use this technique.
If the rules reverted back to starting with both feet on the rubber their speeds would drop-----plus they probably wouldn't jump so far that their knuckles hit the batter in the face.
Here's an interesting thought for all-----check out the speed of your girls using the normal high school rule of only one foot on the rubber---then check out their speed using the ASA rule of two feet on the rubber.
Most high school pitchers don't really take advantage of the one foot on rule and get the running start like the men do.