"I'm guessing it is Standard
You are saying that you move your body forward without leaning. I would say that leaves me still verticle and not imbalanced. So where does your imbalance come into it"
There is imbalance because the body, from the knee up, becomes entirely forward of the standing foot. This means it is not balanced over the only foot bearing weight, which means it is not balanced.
Because the body is vertically aligned from the knee up, no leaning has occured.
You must learn to seperate the idea of leaning (bad) from moving the body weight off of the standing foot while maintaining vertical alignment (good).
Yet once again, I will refer you to frame 2, extension in the learning center forward walk. Although that sequence has some problems overall, frame #2 shows this unbalanced but vertically aligned position that you do not yet understand.
"Would you also like to repeat one of your former statements that in Standard the body goes ahead of the foot so that we can go to our DVD's and in slow motion see for ourself."
That it does and must is the critical concept you do not yet understand. Again, see the referenced image and you must realize that body forward of the standing foot (and hence off balance) is precisely what has been illustrated.
Can you still not see how this does not involve any leaning?