A few rules to consider, when the pitcher steps on the pitching plate: (paraphrasing)
1.) hands must be apart (ball in either free hand or glove)
2.) then. hands must come together and pause for 1-10seconds
3.) after hands separate again the pitch must be delivered (and not come together again)
I see no violation in what youve described, as long as the hands come together for at least one second, before delivering the pitch.
Thanks! Yes, I see now in the rulebook nothing about "pausing".#2, there is no requirement in the rules to pause after the hands come together. The hands may be in motion when they come together, and they may remain in motion while they are together.
As to the original post, if the pitcher brough the hands together, dropped the pitching arm back, came back up and dropped it back again it would be an illegal pitch. After the hands have been brought together and separated, there can be no reversal of motion once the pitching arm has started forward.
There is 1 rule set that I believe does require a pause after the hands are brought together. If Im not mistaken the ISF rules require a 2 second motionless pause after the hands are brought together.
Forward motion and windmill motion are more or less synonymous as they apply to the rules. Forward motion is required for the windmill motion, but the slingshot pitch is also legal. The rule is simply stating once the hands separate, the pitching arm can be dropped to the side and back. But, once the arm starts forward it cannot stop or reverse direction.