Not confirmed but it's sorta obvious, the dialogue and date only exist as part of the Legendary ending, thus it is saying that the dialogue between the Forerunners is from 97,368 BCE while Atriox is in the present day and freeing the Endless, the dialogue and date is shortly after the firing of the Halo array and shortly after the Forerunners found the Endless.

Plus Atriox has no way to go to the past.

If I remember correctly, the writer of the article suggested Atriox learned how to get to the past from the boss-lady-alien we fought (can't remember her name) and freed them there. I guess we will find out for sure in the coming months!

I have no doubt that the writer of the article is wrong, lol.

It's like the Halo 4 ending which was set in the present day but had Didact speaking over it, except this time 343 has attached a date to the dialogue, both things which only exist in the Legendary ending so the date is 100% for the dialogue.

Atriox went to Cortana and got blown up, went missing and was assumed dead, the ending reveals he isn't dead but actually somewhere deep within Halo and about to unleash the Endless.

The date is from when the Forerunners locked up the Endless so if Atriox just strolled in, the Forerunners would still be there and end his life in a second, plus the huge time paradox that unleashing them 100,000 years before would cause.

I'd be fine with any and all paradoxes if Chief and Cortana can be married.

Maybe Atriox should win

Curious, could the Harbinger be a Precursor? Has it been confirmed what she is?

More than that, maybe he should wed them. I could see it now:

Atriox: "AND DO YOU... DEMON... HEHEHEHE... TAKE THE CREATED TO BE YOUR WIFE?"

Masterchief: *Agreeable silence.

Atriox: "AND DO YOU... CREATED... TAKE THE DEMON TO BE YOUR HUSBAND?"

Cortana: "Like I've always wanted to... Yes."

Atriox: "THEN I NOW PRONOUNCE YOU HUSBAND AND WIFE. YOU MAY NOW DISCONNECT THE COMPUTER CHIP FROM THE VISIBLE SCREEN AND REINSERT IT ON THE BACK OF YOUR HEAD."

Masterchief: *does as instructed

*Random combination of humans, Spartans, Covenant, Banished, prophet worshippers, forerunners, and even flood start applauding.

It is curious how she never refers to The Endless as her people, only calling them The Endless. Maybe she is the last precursor and wants to free the Endless because the precursors intended for the Endless to take the Mantle, not the Forerunners. Dunno. 

Harbinger's Cylix also doesn't look like the Cylixes for the Endless that Atriox finds.

Harbinger

Endless

Doesn't she refer to them as "we" near the start?

I'm fairly confident she is an Endless, though who knows if they have a connection to the Precursors, I don't think she is the last Precursor...Unless Primordial lied, also the Precursors intended for Humanity to take the Mantle which is one of the reasons that Forerunners drove them to extinction.

The mission description for the last level confirms that Harbinger is an Endless.

"Chief and the Weapon reach the Silent Auditorium, once the seat of Cortana's power, now claimed and controlled by the Harbinger. Their enemy reveals the Auditorium was where the Forerunners passed judgment upon her species, the Endless, and sentenced them to indefinite imprisonment inside Zeta Halo. The Harbinger sought to utilize her uneasy alliance with the Banished to free her people--a plan that nearly succeeded before it was disrupted by the Master Chief. Finally defeated, the Harbinger says her people have been found, and that the Endless will, at long last, be unleashed. The Reformation is averted. The Auditorium begins to collapse. Chief and the Weapon escape through a portal to an unknown destination."

But that doesn't mean the Endless can't be connected to Precursor in some way.