I don't see anything about 200Hz on that site, and I looked at a few different servos.
I suspect (from other Threads here) it refers to the internal frequency at which the servo updates its position in response to the regular 50Hz pulses from the controller.
You couldn't rely on the new servo command overwriting the current command. Even if it did it would mean that your code would have to update it very frequently which is the opposite of how the system is intended to work.
If you really do need a 200Hz pulse rate you will either have to modify a copy of the Servo library or (which is probably easier) write your own code.
...R