The swing creates the finish, not the other way around. If the ball position at contact is extreme left and you have high level upper arm rotation, you'll naturally finish where you should, assuming your arm is relaxed!
If you try to force the right finish without the correct elements you probably stress the arm a lot more.
I do think if everything is right you can key on the finish as the last point in an extreme left to right swing. But the toss, the racket drop and the less rotated, more sideways body position at contact are the foundation to the kick.
That coach could have a limited understanding of the kick--or he could have noticed that the op didn't really have the correct elements for the extreme right finish.