Is the protagonist's name actually "Nier" or is it just fanon?

[Amygdala]

In the original Gestalt/Replicant you choose your name with no default, but I see people referring to him as "Nier", even the wiki says Nier (Father) and Nier (Brother)

Is there an interview or an artbook where it's said?

[Thaumcaster]

https://twitter.com/RekkaAlexiel/status/1342469703977955328

[RAWRmonger]

It's his own fault if they don't give him a default name now, then.
Personally, I always prefer to have the default thing, I don't wish for self insertion or such vane customization. Having to input my name only means I'm stuck googling what's default.

Specially jarring because, even if we follow the community's "default", we don't know if it's "Nier" as normally written name or "NieR" as the title's official entry on Steam suggests.

[Perdomai]

He never had a official name, but Yoko Taro was told to give him a name when he wrote the novellas so he begrudgingly used Nier