Edit: The Last Secret has been discovered:
In the 14-page article on NieR:Automata in Famitsu magazine Issue No.1527, the development team (namely Yoko himself) dropped a massive hint about a bug that was never fixed in the final version of the game which allows you to zoom-out the camera while manipulating the directional pad and R3 buttons. By doing this, it will bug-out the camera and allow you to see outside the usual scope of what you would normally be able to see, revealing some rather “NieR-esque” things.
The news of the “last secret in NieR:Automata” has been reported on repeatedly, but I’ve noticed that some of the information has been garbled over time. To set the record straight, here is a direct translation that I made from the article:
ーIf there’s any subject on “NieR” that hasn’t been discussed yet, could you share that with us?
Taura: Without entering into the options menu, there’s a specific trick you can do to change the camera distance with the arrow keys while holding down the R3 button.
Yoko: But please use it with caution since it will cause the camera to bug-out and clip through the terrain. After some discussion, we decided to leave it in since it felt pretty “NieR-esque” anyway. They haven’t found “it” yet, have they?
Negishi: No, no one’s found “it” yet. I think it would absolutely be devastating if somebody discovered it, so we’re not going to reveal what it is.
Yoko: There were various circumstances with different specifications, so it’s still a bit unbalanced (in terms of the programming).
ーWhat!?
Yoko: I can’t really talk about it in detail since it’ll get me in trouble, but just imagine this as the last NieR:Automata secret.
According to this passage, it’s clear that they are speaking mostly from a programming aspect. When they essentially say that it would be “bad if this secret got out”, they’re commenting that it would be bad for Platinum Games and the programmers who were unable to discover the cause of the bug, were unable to fix it, and merely left it in the final product of the game without fixing the bug. That could very well tarnish their reputation as a company, which is why they would rather not discuss or even disclose the details of the bug.
However, unlike many reports and references by fans about this information, absolutely nothing was stated about the “fans not liking something” if they found the secret. I believe this stems from an inaccurate translation that was then spread by word of mouth, which eventually took on a whole new shape in the end. Hopefully the translation here will help clear the air and set the record straight about what they were really talking about.
And apparently this so-called “secret” has yet to be found! So, get out there and play around with the R3 camera bug… but be gentle to Platinum Games if you actually *do* find something incriminating.