OK, I've never noticed that (at 14:34:30 or so you can see the crane being copied, that's more explicit and visible if you put the speed at 0.25). It is to note that while the Ultimania said they were in the Lifestream, it pointed at the in between their fight against the whispers and their fight against Sephiroth didn't they? If someone can fill me in about that!
This... would be one of the proofs that... the Lifestream is at the heart of parallel timelines to me. The Whispers being able to recreate/copy elements, and maybe fumble sometimes along the way (oh it's good enough) would explain why we can *see* that there are several Midgar. It definitely shows that it's not a timeloop though and that we are talking about connected timelines through the Lifestream. But I think the singularity is *what* created the new parallel timeline, or at least the one where Zack is seemingly alive. It's like a Big Bang and a "turn right" theories mixed, for Doctor Who fans. We already had OG Midgar and Remake Midgar and now we have Terrier!Midgar. It's the Midgar the Whispers are able to create so that a new reality comes to live.
Basically, Sephiroth going back in time would have created the Remake timeline, and the team defeating the Whispers created the Terrier timeline (see
Ody's magnificent graphics that I think is going on). So we have 3 different Midgar. Both Sephiroth and Aerith have their knowledge of future events from the OG timeline. The Remake timeline is made to interconnect the Compilation, to encapsulate it and gives nods to it. It implies that all events before, during and after the OG have/are/are supposed to happen (most will, if we go by the devs' words).
This also gives another thing to look at for Sephiroth: he was controlling *some* Whispers: what if he wanted to create HIS own reality, and Aerith countered it with the portal he made... I'm just thinking... he wanted them to go through that portal to be able to create his own reality, but Aerith turned it into
her reality (hence why Zack lives)...