I have been thinking about it from a perspective aspect.
The camera is to the left/rear of the swordsman. We are seeing a flat image, not three dimensional.
What appears to be movement from the left to the right is the left to right vector component of the balls trajectory when viewed from the camera position.
When viewed from the the swordsman’s position, the ball is coming nearly directly at him, passing in front of him, from right to left. Notice that his feet do not shift until after the ball has been cut. Post 8 in this thread shows the action in alternating real time and slow motion. The slow motion shows what I have described very clearly.
Lol! it really doesn’t matter in the larger scheme of things.