I guess what I'm trying to say is that by defeating the Whispers, Cloud and the others altered reality around them such that the events the Whispers tried to interfere with and force were undone and their influence removed. I don't think they physically jumped to another FFVII world/timeline but rather changed their own existing timeline instead.
Mako, we haven't seen what happened after Zack and Cloud got to Midgar, so there could still be other ways for Cloud to get the sword. Allow for the unknown and stop limiting yourself to the OG canon. The point of the ending was, in part, to say that things will be different and diverge from that canon in ways you can't possibly imagine.
That still doesn't explain the paradox, and now you're essentially speculating on
unknowns of unknowns that are unknowable and without any tangible evidence or a hint of indication.
What we see is a clear delineation of two timelines. Split apart due to the destruction of the Arbiters of Fate.
What you're talking about is a raw, temporal paradox existing in one single timeline. If you go back in time within the current timeline you inhabit, and you
kill your dad before you were born, then you erase yourself. Because you've destroyed the chain of events leading up to your birth.
Zack being alive undoes the events leading up to Cloud Strife being the Cloud of FFVII, period. And unless you're able to clearly showcase how such a raw contradiction is possible within the text, I don't see the point in arguing it's the same when the ending clearly demonstrates they're not the same timeline.
I doubt they'd go this far, but it is possible that the party changed the world around them without changing their own personal timelines. They'd basically be plopped into a new version of their own world, and with them leaving Midgar, never even realize anything had changed. There are no paradoxes involved that way.
I just know, in my own opinion that this new reality has to have some major relevance to the plot. I abjectly refuse to believe otherwise, it would be completely pointless to show all that, to include the scene with Biggs and the hint about Jessie, if it wasn't going anywhere. Square has made many a questionable decision in the past, but they aren't that stupid.
There's absolutely no way they would be able to undertake FFVII without bumping into the paradoxical consequences of them being in a radically different world that's a raw paradox.
Think about what would spin off from that conclusion. It should be obvious on it's face.
I'm sure the writers can bullshit their way into making it happen. Not that I'd be a fan of it obviously but y'know.
Like, what's your point? Parallel timelines are somehow any less bullshit? All of this is some mental gymnastic backflipping bullshit, we're just arguing which one stinks the most at this point.
That's like trying to balance an elephant on the head of a pin. I'm sure through some theoretical, and experimental physics it could potentially happen but on it's surface it does not lend itself to reconciliation, at all. They're diametrically are opposed.
And there is a huge difference; one is contained to the ending and showcasing the reconciled plot-line that was introduced for Part 1. The other is a continuous narrative that ends up being the entirety of the plot. Those are very different outcomes.