[MizunoJoe]

If your left arm is tight to the chest then the Hands can not accelerate any faster than that amount which the rotating pivot will provide. If however the left arm separates from the chest , accelerates away from the pivot .....then more hand speed is possible. Be it from CF Throwout or Right Arm Drive OUt.

Since there is no #4 in Hitting, there is no pivot, so if you pinned your left arm, the right triceps would have to push the whole left shoulder girdle out of the way, rather than just the left arm.