[whip]

Too bad HB's Physics article didn't include hand speed, but I think you can extrapolate it from the pro and am1 lead arm graph(blue), which decelerates rapidly through release. It would be hard for the hands to continue at a constant speed while the arm to which they're attached, is decelerating. The reason is that as the left wrist uncocks, the left arm is dragging an ever heavier load as the shaft and left arm head toward the in-line condition. Note that amateur 2 actually speeds up his left arm during release, which seems like a good idea(who here hasn't tried it, including me some time ago! ), but is not.

Does any of this data show that you can't have a constant handspeed? No