In these two videos, they do not "hold the extension of the punch." They retract it.There's a correct way to hold and extended punch in a fight and a wrong way to do it. LOL it's people like you where I want to just put gloves and hit you and say "It's like that" lol
This is especially for you. The part about driving through with the puch. People who punch heel down understand this. If I'm going to drive a spear through someone then I'm going to push with my leg instead of twisting and pivot on the ball of the foot like boxers do.
Again the jab doesn't pop back