Not redrawing the parts of the screen that don't need to be redrawn. There's going to be a tradeoff between the amount of works the terminal has to do parsing the input stream, the amount of work the terminal has to do to redraw/update its own buffer, and the amount of work necessary in the program to compute the necessary move commands.
To be fair, the effects shown here update such a significant part of the screen that tracking the diffs might be bigger overhead than a full-screen refresh
IIRC, ncurses does this under the hood.