I think I wasn't clear. I was talking about in a series of strikes. After you punch with the right, it should be coming back while the left is going in, not just hanging out there doing nothing. It doesn't mean the right goes backward every time the left punches.
I've seen it work well to correct students who were NOT getting any leg/hip/body into the punch. This drill makes it easier for me to get them to use more than just the arm. It has the disadvantage of not letting me work with leg power at that point, but many beginners aren't ready for that yet, so I'm okay letting that wait a bit. I don't doubt that some folks over-practice this type of drill to the exclusion of other drills. That would probably create that bad habit of rotating into the punch (that drawing back before the strike you mentioned, if I'm understanding you right). I see that without this drill, too, though. It's not uncommon, when I just teach punches from a fighting stance, to have someone want to draw the hand back before punching. They want to load the power, then deliver. This drill, actually, can be used to help cure that.
I think you're seeing the drill differently than I see it, MD. The hand should NEVER draw back before punching. The opposite hand draws back during the punch (as the body rotates, to chamber for the next punch). So, there should never be a telegraphed motion involved. These are typically done with a pause between punches. The pause, however brief, should be the neutral starting point, and the punch should fire from that pause without a wind-up or telegraph. That's something I specifically use this drill for sometimes - to train OUT that habit to telegraph. The larger motions and squared stance often magnifies the error, so the student can feel themselves doing it - which they sometimes do not feel when in a fighting stance.
That's rather my point. Chambering isn't a unique proposition, in any way. When a boxer jabs, he returns his punch to the chambered position. When he uppercuts, he returns to the chambered position. The chambered position is simply the position from which the punch is able to be fired. I can't deliver much power if my arm is more or less fully extended before I start the punch. But if I keep it bent to some useful angle, it's already chambered and ready to punch with.