[6.0 - 6.4 Spoilers] An interesting video detailing Venat's polarizing reception

[Cleretic]

NieR does not make use of the unreliable narrator method.

...yes it does. Yoko Taro games in general do that a lot, to the point where even the raids he wrote for FFXIV do it at least twice; I'd say unreliable narration might be the main hallmark of his storytelling style through the years. Automata might even be the worst about it, one of the most common plot beats in Automata is 'learning someone lied to us both as characters and people'. Perhaps one of the big turns of the back end of Automata is when we finally get to play as a character that's being honest to both us and themselves.

I haven't played Reincarnation (if you have that would be a wonderful asset to bring to the table here), but from what I've been told and learned about Mama, she's... well, also a liar, albeit mainly in the context of the actual story of the game. When it comes to the context of the collab--basically, a story she tells--is that she's flowery, but detached: she'll big up this story, but it's ultimately second-hand, from a person who cares more about dramatics than veracity. Basically, it's someone telling us Emet's story, as told by Emet... which is how we got it in the first place. So it contains no new information, and anything that appears new could easily be explained as Mama Being Fancy.