1
IIRC, Saski said there were two keys to his forkball. 1) Jamming the ball as far back in to the crotch of his fingers as possible, fingers splayed wide, and 2) Throwing it as hard as he could.
So maybe it's not the long fingers so much, as getting spread between your fingers. Piano players who start young can spread their fingers way wide... It's just like doing the splits or touching your toes, you gotta do lots of stretching, and it's best to start early. My guess is most ballplayers never spent any time stretching their fingers out.