That's all fairly similar to my interpretation of the time-travel-via-dreaming that we talked about earlier, the "reality is all informational" thing. In many of my dreams, when things go a way I'm very unhappy with, I feel like I can "rewind" the dream and re-tell myself the story I just imagined in a different way, where things turn out differently. I interpret the player-character of Eternal as doing that as well, albeit possibly prompted or guided by external forces who are aware of the dream-nature of his reality (like maybe a Durandal-Thoth who transcends time as well).
In my philosophy of time (the actual one I believe in, not just a fictional idea for Eternal or something), a timeline is just a path through the configuration space (or phase space if you like) of the universe. Adjacent "times" are actually just "possible worlds" that differ by the smallest possible amount. We perceive less-entropic possible worlds as in our past because memory-formation, like all physical processes, increases entropy, so the pattern in our memories is necessarily of a universe growing more entropic. So "from past to future" is just the direction from less-entropic to more-entropic in the space of possible worlds, the configuration space of the universe. Due to the statistical nature of entropy, there are necessarily more higher-entropy states than lower-entropy ones, so there are necessarily more high-entropy then low-entropy possible worlds adjacent to any given possible world, which means more alternate futures than alternate pasts for any given moment, which means that futures diverge over time (over distance in the configuration space), and pasts converge over time, which is why the past seems constrained and the future seems wide open.
If it were possible to step out of that system in its entirety (which I don't think it is in real life, but I take to be the case in the fictional Marathon universe), "traveling through time" and "exploring rearrangements of reality" would be tantamount to the same thing, because other times just are other arrangements of reality, a special subset that bear a causal relation to the arrangement that we call the present.
