I don't remember seeing this but I'd like to make a quick comment on it that relates to my post above.
The reason people don't punch from the hip in sparring, or indeed even in a real fight is because it isn't effective for the intended goal. People in a fight have their hands up covering vital areas rather than chambered on their hips. And if one understands and accepts the in-depth application explanation for this, the chambered hand on the hip isn't related to a punch at all. Not even remotely close to a strike. It is a grab (clothing, limb, head) and bringing that item back into your center while turning your wrist to off-balance which then sets the person up for a lock, throw or actual in-close strike. Those in Karate, Hapkido, Aikijujutsu, Chin Na etc do this movement all the time, they just don't use the forms as instructional aids. I use this same exact movement all the time on-duty to bring in a control a subject. That is why I can look at movements such as this and just 'see' the application that was originally intended (at least from the Okinawan perspective). This is just one example of where the b-p-k methodology breaks down completely or at least fails to address the movement from a realistic application. One can believe if they wish that the hand is chambered on the hip for the execution of a straight punch. But then I'd have to simply and respectfully ask...why don't you spar and/or fight that way? That movement wasn't just tossed in for grins. It has a meaning that is suppose to work in a real fight against a real, determined and resisting opponent. Just tossing some things out for your consideration. YMMV