What does the arrow in the bottom left corner do?

When watching someone's drawing bring drawn, in the bottom of the drawing area (above the letters) there are two icons.

I know the one on the right, which looks like two arrows around each other, shuffles the letters around.

What does the one on the left do? It looks like a curved arrow pointing to the right, but I've not been able to notice any function. I thought it might be to redraw the opponent's drawing, or to skip to the final result, but it never seems to do anything when I press it, either while the drawing is in progress or when it's finished.

That arrow recalls all the letters that you've put down so far. So try guessing incorrectly, then pressing the button; all the letters will recall to the letter cache.