You may not remember, but @riseball and I had a long discussion about this several years ago. He was adamant that a player could get movement by changing the finger pressure on the ball. At first I disagreed with him, but he convinced me that something was going on.
With the caveat that there are some obvious, major differences between softball and baseball pitching, finger pressure absolutely is a HUGE part of how Major League pitchers are developing new pitches. Couldn't begin to guess at how the differences would change the impact of finger pressure, but all that stuff matters. Which finger touches the ball last matters.
If it's possible to do some of the same stuff with a softball as you can a baseball, the next 10 years of pitching are going to be wild.