With circular punches in kung fu the circular movement is used to redirect and to counter. if you throw a straight punch I'll use a circular motion to redirect that punch and to counter. The circular movement allows me to use the momentum of one circular movement to feed the movement of another circular movement.
In Jow Ga the fist is not mad the same way as it is made in boxing. We do not wrap the thumb around the knuckles and this allows us to hit with the 2 different sets of knuckles (the knuckles boxers hit with and the knuckles we use to knock on a door) and the flat part of the fist which is made of the palm and knuckle. Making a fist this ways changes the alignment of the bones in the hand. Shown in the video below
Our hooks which are in a similar motion as the hooks that he has shown. We throw our hooks in a forward facing stance and a side ways stance. Our techniques when using these hooks target the soft and vital areas of the head. It is my belief that the founder of Jow Ga fought a lot of Wing Chun fighters as our techniques seem to mess up the concept of A to B being the fastest route. A to B is only the fastest route if B does not move before the hit. If I throw a circular punch at the same time you throw a linear punch then I can land my punch first provided that I move in a different position. In the video below you can see a circular punch beat a direct punch by moving B
The other thing about the circular punches of eastern systems is that they have a tendency to go outside a persons field of vision so for a short period of time the person is unaware of where the punch is. Curve punches often strike around a person's guard. This can also be seen in the video. I don't hate or think that straight punches are weak. Because we use quite a few of straight punch. A circular system doesn't mean that all the punches used are circular.
When I watched the video my assumption was that he was only talking about the curve punches and straight punching from early western boxing. If so then that means some of his comments about circular punches won't apply to circular martial arts. The only thing that applies universal, is the theory about the straight linear punch, provided that B does not move while the punch is being executed.
Straight vs linear is often viewed with the assumption that one is better or faster than the other instead of viewing them as a tool of attack that works well this way or that way. If your goal is to hit the front of the face then the jab is best for the task. If the target is to the side of the head then the best attack is a circular one. A person can break their hand just as easily from a jab as they can from a circular punch. For Jow Ga, a person is probably more likely to damage their forearm and soft tissue areas on the arm from a circular punch as a result of hitting the elbow.