Inconsistencies with the sundering (Spoilers)

[kpxmanifesto]

The battle between Zodiark and Hydaelyn still happens, it’s just not shown in that one weird cutscene.

And that's why the OP is calling it a retcon. Such a crucial and definitive moment in the game and the writer forgets or refuses to add that in?

If we’re going by the “official” definition you provided, then this whole game was retconned in ShB when it was revealed that the Ascians are Ancients. Or when we find out that Zodiark and Hydaelyn are primals. Or when we find out in post-ARR that Ascian powers are also the Echo and later in ShB that it’s due to some soul memory thing. Or in SB when we find out that Emet-Selch was Solus.

This is a textbook example of Reductio ad Absurdum. It's not going to work here.