Re: redisplay-dont-pause is not mentioned in the Emacs manual

[Richard Stallman]

        Normal redisplay is restarted whenever it is interrupted by user
        input.  For example, pressing and holding the down-arrow key will be
        "randomly jumpy" -- depending on the speed of the computer vs. the key
        "repeat rate" of the keyboard.

Emacs defers redisplay to input to make sure it does not 
fall behind.

        The only way to get "more fluent" display updates is by setting
        redisplay-dont-pause.

I can't imagine what you mean by "more fluent" display updates, but if
you observe that the keyboard key repeat mechanism is causing
redisplay to be pre-empted, it means that keys are coming faster than
Emacs can redisplay them.  If Emacs does not pre-empt redisplay in
such a case, it WILL fall behind.  And when you take your finger off
the key, you will have to wait some length of time for Emacs to finish
executing and redisplaying the keys that were buffered.

The value of redisplay pre-emption is precisely for cases like this.