Henadic Theologian
Legend
So, the whole central shtick here are the time-wimey obelisks of timeline resetting, which have apparently already been used by Vecna prior to Icewind Dale and the Shattered Obelisk: this is not a static Newtonian time approach.
Mage: The Awaking and Star Trek both have the ideal of things that for various reasons don't when timelines change.
In Star Trek its stuff with Temporal Shielding and various other effects that shield people and objects when their timeline changes. Everything changes around them, but it doesn't effect them even if it does mess with causality. Example was Annorax's ship, even when he destroyed his own civilization's past his temporal shielding protected him. Another example in First Contact was the Enterprise E being protected by I think the energy trail of the Borg traveling back in time to assimilate earth.
In Mage: The Awaking countless Gods, like the Exarches and Archmages, perhaps other beings like the most powerful True Fae, have just absolutely screwed and completely rewritten history so many times, that the world is litter with places, artifacts, and people who come from extinct timelines, but survived into the current one, called Achronisms.
So my thinking is Abeir and Toril, heck maybe all of Realmspace, will be shielded by AO or the Council of Greater Gods, or heroes, from the timeline changing effects sweeping the rest of the multiverse, leaving Realmspace a giant Anchronism in the current multiverse, including perhaps remembering what the multiverse and other world's histories look like.
And AO does have that power, remember AO seems to have pulled FR out of the common multiverse and into its own for 3e era, as well as splitting worlds and merging then, creating pocket planes, stripping entire pantheons of their divinity for a time, creating Gods and blocking unwelcome Gods from Realmspace, ending the Dawn War, I think he created FRs crystal sphere, etc..., so blocking a cosmic retcon/temporal wave is within his power if he choses too, no matter what Vecna does with the Obilisks, at least within Realmspace.