I remember way back when I started windsurfing on a lake, I was standing up to my knees in water on the nose of the board trying to push the nose off the wind and still not succeeding.
The problem was that the centre of resistance moves forward as your weight moves forward, so moving the sail forward isn't all that is involved. You need to get a twisting moment going through your feet.
So
you need to get more push through your front foot and that means more pull on your front arm. That will push the nose off the wind.
When planing and in the straps, more force through the mastfoot helps push the nose off the wind.
Here he moves the sail fore and aft, but notice that he doesn't move his feet - that's how he gets the twisting force that turns the board.