This video has a number of issues. They are correct that technique is important as Wing Chun is all about the domination of an opponent using technique. They are also correct about hitting on the centerline so that the opponent can't disolve the force by turning. However they only half understand the point of putting your elbow behind your fist. It is true that putting the elbow behind the fist maximizes power being delivered in this style. However other systems could easily argue that they can get a more powerful hit in doing a round house punch or something similar where the entire body is twisting. In wing chun the elbows are kept in in order to maximize the power while staying rooted to the ground. Punches come in an upward direction so that the recoil, which according to Newton's laws of motions must be equally as large as the power delivered to the oponent but in the oposite direction, is directed back through the stance into the ground. Thus in Wing Chun, the harder you hit the more rooted to the ground and hard to push off your stance you become. Furthermore, the connection to the hip is not explained at all. Wing Chun stacks the elbow behind the fist in order to connect it to the hip. It is then possible to deliver an incredible amount of power with the punch by simply turning the hip slightly as you punch. This give Wing Chun a portion of the round house power other systems might use but without loosing the square of your shoulders to your oponent or disconnecting you from the ground. However, you can't do this if you stand as the figure in this video does.

In the video the figure attacks with his front foot pointing towards his opponent and his back foot pointing out to the side. This is exactly backwards. He should have his front foot turned in so that his opponent can not easily attack his groin and so that his natural reflex of lifting his knee, if his groin is attacked, puts his knee in position to protect his groin. Furthermore, and perhaps even more importantly, his mobility and power are greatly reduced by having his back foot turned out. The back foot should be pointing almost completely at his oponent in order to give him the ability to connect the punch at the hip. With the foot turned out there is no way to connect the left punch to the hip and so power will be greatly reduced, and his ability to turn should the opponent step to his right is also reduced.

Finally, the attack in this video is towards the chest. While it is good to hit the chest it is much more effective to hit the head, throat or nose. With the upward direction of the strike it is much harder to block the attack and it is also much easier to slip it through your oponents offenses. Since the punch comes in a straight line the Wing Chun practicioner only needs to open a small hole in the oponents defense in order to get a strike in. By making strikes extremely fast the practitionar maximzes acceleration and thus maximizes the a in F=mA and thus in accordance with Newton's laws of motion. By connecting at the hip and to the ground the system maximes the connected m as well providing devistating force without giving up grounding or position.