I'm not sure that a CIWS engaging a surface target is in the same automatic mode that it would be engaging an inbound missile. The addition of optic tracking would seem to mean it's being tracked by a gunner and not the radar/computer. I'm not positive on this, the last ship I was on did not have this upgrade at the time.
What appeared to be the case in the video (start watching at the 2:00 mark) is that the boat seemed to be far enough away that there was about two seconds between hearing the gun shoot, and seeing the rounds impacting the water. A rapidly zig-zagging boat can move out of the target zone.
A boat may be thus able to get close enough to launch a high-velocity rocket at the ship.
Or perhaps an anti-ship missile can zig-zag until it gets to within a certain distance, and then hit full power on the rocket to close the final half mile very fast.