The premise operates off of the concept behind Schrodingers’s Cat. Edit: seems like I have to point out that this use of the idea is more complicated than the theory. As the text theory doesn’t include time travel and multiple isolated domains of uncertainty. Which since we all played the game, I figured you knew to take that into account but it seems no one did. https://en.m.wikipedia.org/wiki/Schrödinger%27s_cat How does it apply to make this work? The Forest is a House, isolated from the material universe’s time. Within the House are rooms, the various simulations and locales within the Forest. Saint was wounded in room 1, went into room 2 and died. We traveled back in time, went into room 1 and saved him, he goes into room 3. Because the rooms are separated, room 2 isn’t affected by room 3. Thus allowing the Dead Saint to still exist. This is contradiction is why Osiris targeted the Forest, the extra layers of isolation uncertainty created a way to cheat time. Furthermore, when compared to saving Younger Saint who was in the material universe’s timeline, we don’t see two Saints because he’s not in an isolated place that allows uncertainty. The differences in outcomes is wholly explained by this more complex version of Schrodinger’s idea. The simulations within the Forest are isolated domains, that’s why you need gates/portals to move between them. Just as the Forest exists outside normal space and time. Some sims are in the past and future, some are in the present. They run independently of each other and that is the technicality the Sundial exploits. So the area where Saint died is separated from the location where we saved him. This is where the magic happens for Schrödinger to work. In one domain he is dead and in another he lives and that’s the one that walks out. Both are original, he both died and lived. The Perfect Paradox. And when you read Missing Pages, you see how Vex influence can alter memories. https://www.ishtar-collective.net/records/clovis-brays-logbook-missing-pages So when Maya gets ahold of Echos Control power, she is able to exert influence on Saints memories. Just like regular vex could do to humans and Exos. Adding Control explains how this works on Saint. It’s two things rolled into one.