There’s a three day time skip which gets a lot of focus put on it. Why bring it up if it’s not relevant?
The final cutscene talks about the Endless and they cannot be allowed to master time as it is not a construct the Forerunners can control. Flowery metaphor only?
They decide to date the Legendary ending 98000 ish years in the past. There’s no reason to assume that’s just due to the text because there’s no reason to do it that way. Date usually signifies what we see not what we hear. If Atriox went through a portal then like Chief there was likely a time dilation effect but many orders of magnitude greater.
There’s a Forerunner audio bit where it says there is evidence of a non Forerunner species living on the ring before the Forerunners. That is impossible as they built Zeta Halo.
A lot of emphasis is placed on how this ring is different and it’s purpose unusual. Cortana wanted something from the Endless as did Atriox. What could that be? When Cortana first discusses this she says “You know what I want” which is peace and to get John back; if you have a time machine you could engineer that. The Monitor in the audio logs talks about rings within rings. Along with hidden warnings within the machine and who left these and why?
Several characters make the recurring analogy the Halo ring being an Ouroborous. The snake eating it’s own tail and this is usually a symbol of time. Time being Endless and Infinite.
In the fractures event they use the image of a broken ring much like Zeta Halo to symbolise the breaking of time into these Slipspace fractures. So Atriox going back in time could be a Slipspace fracture or time travel.
They have an event in game referring to Slipspace fractures and alternate timelines.
An armour skin description for the Tenrai armour heavily implies Jorge from Halo Reach got sent through the Slipspace portal to the Samurai universe. Yes it’s Jorges colour scheme.
The ring is described as having disappeared and the Banished as being stranded? How? They have comms and Slipspace drives. It should be easy to leave and find out where they are. This suggests something very strange happened. There’s only reference in the audiologs to the explosion at the Silent Auditorium (do you know it’s true purpose as Atriox asks) no mention of it entering Slipspace. So, Zeta Halo is a time machine.
In general, Halo is heavily inspired by 80s sci fi. It’s not that off brand to copy Terminator or Back to the Future. Especially Terminator. They even gave Atriox a half destroyed face like a Terminator. They sure want us to know Chief thought he could talk Cortana down; just saying.
Also, for what’s it’s worth. Joe Staten was involved in the story for Destiny and that included stuff like time travelling robots and all kinds of bonkers sci fi fantasy notions.
I think it’s more because it would be disappointing if all this mystery and talk amounts to the Endless have no nervous system so decide to fire ring. That’s a boring dead end and the statement on them being worse than the Flood would make no sense.
I am sure there’s others but somethings up.