The thing you need to concentrat on is not watching only how the tip well is thinning out, but WHERE Carl is doing the thinning and blending!
Note that the edge of his file never goes near the natural until the last few passes of the file that remove the last line of the tip-well that is visible.
Note that in doing the above, there is no damage to the nail plate., because he is never touching it!
Note the methodical way he is working file from one side of the nail to the other, rhythmically so that he does not over-thin the tip in one area and not the other.
Note how the tip-well is all blended evenly together and thinned BEFORE he finally gets rid of the last line.
THIS IS THE WAY TO DO IT!