"Anonymous. I suppose a good argument would be that what is past is dead. Therefore the first step only starts as it lands. We cannot turn time backwards. It is gone it no longer exists. All of you scientists have a go at that one. Taking it on from there. Step one starts as it lands. Step two starts as it lands. Between you and me I don't give a hoot."
Don, if you choose to redefine when a step starts and ends, then you have to take all those instructions about what is supposed to happen at the end of a step (commence to rise, lower, whatever) and move them to new portions of your redefined steps, so that they will still happen at the same point in the action as they are formally written to.
It is in your failure to make that translation that the fundamental mistake occured.
If you change the defintion of a step, then you must also change everything else that depends on that definition!