So my daughter's first pitching coach really pushed her leading with her pinky when she pitched. I never understood why, and really still don't,
My DD's first pitching coach teaches pinky first. I believe (and I could be wrong) it is a way to reinforce keeping your hand inside the ball as long as possible to allow for IR. I am pretty sure in one of the Sticky threads, BM and Hillhouse discuss throwing a football underhand to teach the feeling of staying inside the ball as long as possible.