he wasn't getting much into the punch from his hips or his legs. He was drawing it back and throwing it from his arms and shoulders.
Freddie falls into a trap here in his way of explaining things, and it is a common one in boxing and it confuses a lot of people and leads to things being taught improperly. I am not saying he is wrong in the way he teaches it- I have seen him work at his gym in Hollywood and know people that he trained when he first went on his own and was working out of a gym in La Habra. But the explanation is wrong and conveys the wrong sequence for weight transference.
The pivot of the right foot does NOT generate the power in the right hand; it is a result of how that power is generated. The same is true of the left hook; the power does not come from the turn of the left foot, not if you are doing it right. Doing it that way puts the weight behind the punch, which makes it a push. You need to get the weight turned in front of the fist, creating a whip-like effect and concussive force.
To throw a hook, then, the first movement is to get your weight onto the rear leg. You use the muscles on that side of your body to violently wrench your body around. The first place this manifests itself is on the front foot; the violent torquing of the hips causes the foot to pivot inward. The next place it shows is in the shoulders, which turn fully over the rear leg. The fist itself never moves- it does not draw back- until the bodily tension whips it through the target.
If you watch the video, that guy is throwing the hook off his front foot. The weight never gets back to the right leg. This would show up, profoundly, if he were to try and string together punches, another right hand, for example.
My suggestion to you would be this: Exaggerate your movements until you find the feel. Throw your straight left- you are a southpaw, correct?- and really get your weight onto your front foot, then turn through it. You will feel the force I am talking about. Then get your weight back and crank off a hook. You'll find the feeling.
This is very much how Julian Jackson punched. I read an interview with him in KO magazine in the late 1980s where he talked about how he was taught and I stole liberally from what he said.