Someone correct me if I am wrong but the entire mode of construction now seems to have been changed. Previously they would work on a couple distinct floors at a time and so the building would always be "jumping" by increments of two floors.
Now when I look at the pictures I can't tell how much any given beam is raising the height of the building. They seem to have steel beams that span different floors and different heights at the same time. That is, maybe they currently have steel up to the 91st floor yet the new steel they then put in goes from anywhere between 89 and 93, with each beam covering different floors. In sum, instead of having splices neatly ever two floors now we have splices all over the place.
Don't know if this is true but the pics make it look that way. Is it true? And if so, what is the reason? Would it have anything to do with the floor space getting smaller?