Right, then... [Nier: Automata/Copied Factory] [Spoilers]

[MoofiaBossVal]

I wouldn't rack my brain trying to think about how it fits into FFXIV lore. The Copied Factory looks hundreds of years old, and yet apparently that valley had never been found by Amaro riders or airships flying overhead. I'd just say that the events of the raid are a continuation of Nier Automata's story, taking place in the FFXIV game, but not really canon to the story of FFXIV.

[Berethos]

I wouldn't rack my brain trying to think about how it fits into FFXIV lore. The Copied Factory looks hundreds of years old, and yet apparently that valley had never been found by Amaro riders or airships flying overhead.

That we know of, at least in the past 100 years. Remember that the loss of most of their world also led to a great deal of loss of records and information from before the Flood.

During the last 100 years, it's feasible that exploration into what is essentially uninhabitable mountains while most days for years and years are basically a fight for survival wouldn't be a priority. Fighting Sin Eaters, even for the Eulmoran army for most of those 100 years, was mission number one.

Also consider how far into the mountains we are. Were we anywhere nearby, we'd be able to see the massive Talos and Mt. Gulg floating in the sky, and neither are anywhere in sight. So wherever we are, it's far enough into the mountain range to be out of sight of those, which makes it far enough that it's unlikely to have been visited by airships or those flying on an amaro in the last 100 years when society has bigger issues than exploring deep into random mountain ranges just to see what's there.

We're also talking about a completely different world with a mostly unknown past compared to the Source. It's a trifling matter to fit into the FFXIV lore when it's on a world where most of the world's history is a long lost mystery, and with crossovers of this nature they tend to be "This character is this universe's version of this character in some form or fashion, not the character from the original work visiting."

It only becomes tricky when trying to connect two disparate franchises in a canonical fashion...which outside of the unsourced claim that Yoko Taro has said it's canon to NieR's world, there seems to be no indication the creators of this crossover are trying to do that, and instead are handling it like they did with the Ivalice crossover, injecting a version of it that exists entirely within the universe of FFXIV and is simply inspired by the original work, not a continuation of the original work.