Sundering stuff established in the Q&A

[Cleretic]

Yeah, it was all about "controlled opposition".

I've noticed some posters appear to struggle to distinguish the characters pre-sundering from what they are 12k years later...

Okay, so there's something that gives a bit more detail on this one, and it shows better the truth of what happened. From the second Emet-Selch Tales from the Shadows (the 'Azem Vs The Volcano' one):

This was soon after Zodiark became the will of the star, and our Final Days were averted. The people were divided, unable to decide what to do with the future that now stretched out before them. Many wished to trade the new life which had sprung forth to reclaim those lost in sacrifice to Zodiark. No small number, however, insisted that the fate of our world should be entrusted to those selfsame freshly minted souls. All were at our wits' end.

At once, we saw it, shimmering. It poured out of Zodiark's breast, and resolved into the shape of a man. As he looked us over─mouths agape, no doubt─he gave what passed for an earnest smile.

"Fear...not... You will make...the right choice. And I will see it through."

So this gives us a timeframe; this is specifically after the second sacrifice, but before the Convocation were locked in on the third. If we want to put together an actual chronology, we know that the Anamnesis meeting was after this, because at that point the Convocation were certain and unyielding. But, now take into account his line after becoming what we now know is a primal, as well as the heart of Zodiark: "You will make the right choice, and I will see it through."

He's not extending impartiality, he's extending certainty. The assurance that the choice they make will be the right one--and as Zodiark's heart, there was only ever one road he was going to go down. He 'reconciled' by leading people down one specific road--and you can tell from the Anamnesis meeting, the opposing side wasn't quelled, they were shut out.