Interesting take! Where did you read that?
I sincerely hope it's wrong, though.
And, I'm of the opinion that it isn't correct. And I base that assertion off of Advent Children and Crisis Core.
We've already seen all of the foretelling. Aerith (I really struggle calling her that, she's always been Aeris) dies, it's tragic, but it's also part of what made the original so great. Aerith getting to live feels cheap, and her sacrifice means nothing. Besides, we know she doesn't die, since nobody dies, they just return to the planet.
In terms of sending the story in any other direction, i.e. a different path where Aerith still dies, then I'm not sure. All the while playing this part 1 I've been imagining what the Gold Saucer, Cosmo Canyon, Rocket Town, Temple of the Ancients, Chocobo farm etc. will look like fully rendered with the new graphics, and all the other little places in between.
My theory is that extra content at the end of Midgar, i.e. the battle with the whispers and Sephiroth (which isn't actually Sephiroth, as his body is in the Northern Crater), is mostly fan service to whet the appetite of the fans. Can you imagine how much of a anticlimax it would've been just to leave it at the end of them just walking out of Midgar? This way they've managed to squeeze in a fight with Sephiroth, an early fight with Jenova, leave you on a massive high, and also show bits and pieces from Crisis Core. It's all lore, as far as I'm concerned, and all canon.
Where that doesn't make sense if the bit about the unknown story etc. But I think that's just Square Enix toying with us.
Still, an interesting take, and it wouldn't totally surprise me if true. But I know a lot of fans wouldn't be happy with that.