That little video may show something unique to you instructors that are regularly focusing in on other's body positions and techniques, but to me he looks generally similar to some other bump skiers I've seen that are more interested in control than speed and reducing impact. Certainly not your pro mogul technique but hey a lot of us recreational bump skiers don't ski like that. Accomplished ski instructors often ski bumps rather so. Or maybe I'm just not seeing something. The video is short since internet bandwidth is a limitation on videos. The snow or few moguls have only the most vague visibility. I'm sure he could probably smoke a serious bump field way better than me or most of you.
Natural skier made mogul fields have a huge variety of shapes, dimensions, and lines that one must instantly be able to contain. Many shapes in a field are continually evolving growing and waning especially where snow is softer and drier. Some moguls evolve quickly while others are still there a month later. Simply said, control speed to a slower rate and mogul impacts can be reduced to modest levels. Personally I use a lot of subtle upper body movement instead of just leg action below because moving ones upper body, head, arms, and wrist/hands for pole plants can be used as tools to control dynamic edge bite into a slope and manage motion through the maze of shapes. Then again I might move down through several bumps with my upper body absolutely relaxed and quite with just my legs swiveling below. A lot of what my body is doing, I probably have little clue as to what is really going on at a level some of you experts could pick apart. One example: I sometimes like to delay my upper body to move forward over the nose of steep bumps at times which can really help keep speed down at the expense of some dynamic smoothness. Like your moving nicely through a bump field and then one comes to a short steep drop with large bumps before leveling back out again. If one just keeps the same rhythm up, the result may be considerably more speed at the end of the drop.