Do you think after Endwalker there will be time travel?

[Jandor]

A split would mean that the current world and the bad future exist concurrently. There is zero evidence of Graha creating another shard, and a different timeline makes a lot more sense due to the time travel involved in changing things. If he had created ANOTHER shard through what he did someone would have mentioned that by now.

Why? Who would know? Who would say if they did know?

Conscious that others were watching, I shook my head. Causality be damned. I refused to believe our friend would allow our travails to be for naught. The Eighth Umbral Calamity had been averted, if not for us then in a divergent timeline.

That was from hundreds of years in the future, in the Source. Since G'raha was succesful in averting the Eight Umbral Calamity (Black Rose), and there was no Back To The Future change in their timeline (therefore, a Temporal Paradox). It is textbook alternate timeline, not a separate Reflection. As far as we know, only Hydaelin would have the means to create ANOTHER Reflection.

It'd only be a separate dimension on the loosest of terms that would still require it to be an alternate timeline.

He's stating what he chooses to believe has happened. Just as G'raha doesn't really know the fate of that world, they're not really sure of the fate of G'raha.

A separate reflection solves the paradox because G'raha becomes an outside actor, he is no longer interfering in his own past because the events that lead to him changing the past happened on a different world to the two he changes.

I mean, I suppose you could say the Source and the shards are all already alternate timelines in a way. They were all split 12,000 years ago from the same point and they all developed along different lines, sometimes with the timelines of each world being at different points relative to each other, but they're all still linked in the grand overarching scheme of things too.