The nature of the Sundering has been spelled out in a Nier Reincarnation side story.

[Rongway]

I'd say it's a safe bet that it can be taken seriously as canon given that the Nier universe is already directly connected to the Final Fantasy XIV universe via the Nier raid storyline.

No, Nier is part of FFXIV in the same way that FFXII and FF Tactics are part of FFXIV: it is not. Characters and events in FFXIV that resemble characters and events from Nier are not the characters and events from Nier. They are characters and events that resemble characters and events from Neir. In the same way, it's safe to say that characters and events in Nier that resemble characters and events from FFXIV are not the characters and events from FFXIV.

Ishikawa also had a direct hand in crafting it which suggests a desire to acknowledge and maintain a sense of canon alignment.

Until an XIV dev says, explicitly "the events in this other game that isn't FFXIV are canon to FFXIV" or the information appears in official FFXIV material, you cannot assume canonicity.

[Kozh]

No, Nier is part of FFXIV in the same way that FFXII and FF Tactics are part of FFXIV: it is not. Characters and events in FFXIV that resemble characters and events from Nier are not the characters and events from Nier. They are characters and events that resemble characters and events from Neir. In the same way, it's safe to say that characters and events in Nier that resemble characters and events from FFXIV are not the characters and events from FFXIV.


Until an XIV dev says, explicitly "the events in this other game that isn't FFXIV are canon to FFXIV" or the information appears in official FFXIV material, you cannot assume canonicity.

But Nier collab is different than 12 and tactics. FF14 pays homage to 12 and FFT; it borrowed lore, settings, character's names. Meanwhile Nier is a collab where we directly interact with the characters from Nier game. Just like how FF13 and FF15 collabs were. The Lightning and Noctis we met is the original one, even though we may never mentioned it in msq.

[Seraphor]

No, Nier is part of FFXIV in the same way that FFXII and FF Tactics are part of FFXIV: it is not. Characters and events in FFXIV that resemble characters and events from Nier are not the characters and events from Nier. They are characters and events that resemble characters and events from Neir. In the same way, it's safe to say that characters and events in Nier that resemble characters and events from FFXIV are not the characters and events from FFXIV.

This is incorrect.
When Nier was released (or maybe even announced) it was stated that it would be canon to Nier. The events in 14 directly follow on from one of the many endings of Nier Automata, in much the same way that all of the Nier games are direct continuities from one of the alternate endings of a previous game.
YorHa: Dark Apocalypse is canon to the Nier universe.
It stands to reason that any mention of FF14 content in Nier content directly related to YorHa: Dark Apocalypse is also bilaterally canon, especially if it's written by the same writer.

This is markedly different to the Ivalice questline, which IS stated to merely be a reflection of those events and characters.

[Rongway]

it was stated

Please link to the statement.