Not sure why he is jerking his bokken to a halt in front of him.
I see this a lot. IME this is mostly caused by the user stopping the sword
rather than letting the sword stop naturally. Other causes are poor grip, lifting shoulders, and by "cutting air" rather than cutting a specific target. The way I fix this is by keeping metsuke/eyes on the target and cutting (emphasizing power) only in the target area; once the sword has cut the intended target it continues to travel and stops cold somewhat horizontally (depends how good your grip/tenouchi is), with no twitching or jerking at the end like you see in the video.