In Alex Moore's technique book. The very first chart in the Waltz section hasn't been performed that way for many years. The Closed Change, either backward or forward you will see that once step one is in place, step two goes straight out to the side and then the closing of the feet takes place. The way it is done today after step one is in place the now moving foot comes under the body before going to the side. If anyone is being taught or allowed to do different I would suggest they try for themselves and see which is the better and do the same on any simular steps. This now gives us one type of stepping back or forward in any of the Swing Dances. If you put a little pressure when going backwards on the heel of the moving foot you will find it adds to your ability to balance. If we now go to the next page which is a Natural Turn the moving foot passes under the body at the time the turn takes place. I seem to remember some discusion a while back about being able to lift the moving foot off the floor after it is is in place under the body in practise which proves i believe that a person is perfectly balanced. Correct me if I am wrong but it came from a lecture by Andrew Sinkinson. My apologies to Alex, but he did have to write as it was being done in those days. His hands were tied.
When doing a Backward Lock in the Quickstep as you draw the left foot to Lock a little bit of pressure on the heel will not go astray. From there you can find other places where this technique can be applied. IIoka

Pressure on the moving foot might help control a beginner's poorly aimed movement, but with good aim it is wholly unecessary.

As for being able to lift the moving foot off the floor to prove balance. Well, first it doesn't prove balance unless you can stay in that position. Certainly there is a point in each step where (if you were not already moving) you could hold the position indefinitely - you are balanced. But during most of the duration of the step, you are not balanced, for the simple reason that your body weight is not over your only standing foot. It doesn't matter if you lift the moving foot or keep it on the floor - as long as it is not supporting your body weight, it cannot contribute to the physics of your balance.

What a little moving foot pressure could do though is contribute to your SENSE of balance - it uses one of your five senses (touch) to give you feedback to improve your aim, but it does not actually contribute to supporting your body. Again, beginners need that, experienced and well practiced dancers usually aim well enough that they don't need these after the fact corrections unless something unexpected happens.