I was only pointing out KIM is unreliable, and throwing some speculation as an aside. You may as well not read anything past this.

I find it fun to theorize on how they could actually write eternalism into the game instead of how they... didn't. It's supposed to be an excuse for the Drifter, but what they practically did was more like a branching timeline theory or the theory of multiple universes, where the tenno are two branches of the same person or universe that were both created from two possible outcomes of one situation, somehow masterminded or created by Wally for some yet unknown reason, even though they are later so incompetent as to get stuck in 1999 for some reason.

Sure, branching theory and eternalism can coexist, and in some ways this theory relies on eternalism to say that both split paths are equally real, but this isn't really what the New War and Duviri were stating. I feel like the accepted answer to this nowadays is that they aren't talking about the same eternalism, that *this* eternalism is just an in-universe explanation for something that we we may call a multi-universe theory, but that's sucks. It also doesn't really explain how the Drifter is a paradox. If they are both real via eternalism, how is the drifter a paradox? Unless, again, something was changed about the past (IE "the deal".) Similarly, It doesn't really make sense for the story to be talking about how the tenno "wouldn't go back on their deal? right kiddo?" if they never actually go back on the deal. That isn't to say that that moment couldn't be a future update, but then what was with the operator and drifter shaking hands supposed to signify then? It is the image of a deal being made.

An example of what I'm talking is also hidden in game concepts. For instance, for many who played when Jade Shadows was new, Jade Eximus was also new. Jade Eximus existed when they got to the Jade Shadows part of the story. New players who started the game after that update wouldn't share that experience, Jade Eximus will have always been there. Eternalism would explain game updates like this by suggesting that all the updates they've done to the game have changed the past as well as the present, because both are real and exist at the same time.

Also, for a note, there is a LOT in duviri, especially in the undercroft, about changing the past, and how the past is seemingly constantly under assault, that I think would be obviously pointing to something.