Curious about something regarding Emet-Selch ***Endwalker spoilers***

[Sakurakouji]

Emet had (tied with Hythlodaeus; he was just a much better mage than Hyth, period) the strongest aetheric sight of all the ancients (part of the reason Azem and Hyth pushed for him to take the seat of Emet-Selch), and could perceive the unique colour of a persons' soul.

Hades wasn't unmatched in terms of soul sight. Hythlodaeus had the superior ability (explicitly stated in Tales from the Shadows), but he felt his friend was better suited for the seat of Emet-Selch because of his far, far superior ability with creation magic (as you mentioned). His take was something to the effect of: there's no point in having this sight if I don't have the power to act on it. Which is why he pushed Hades for it after he had rejected the seat for himself.

But yes, I do agree that Emet-Selch knew the Warrior of Light is Azem. It's just that, much like how he said he didn't consider the fragmented beings to be people, he didn't accept the Warrior of Light as Azem. There are other instances throughout Shadowbringers, like when he's talking about Amaurot to the protagonist, and he remarks, "Not that you would remember." If you choose to inquire about "remember" he just says never mind and moves on.

To me, his lashing out toward the end of Shadowbringers was because seeing the vision of Azem within the Warrior of Light was basically proof that you truly were the inheritor of his best friend's spirit. Except he's now on the opposite side of the fence, too far gone to rekindle anything. He had to fight to the death with his best friend, and it made him angry.

[Mirhd]

...

I read that back when it was released, which is why I said "tied"; both their sight was far superior to any other ancient by leaps and bounds, so Hyth being slightly ahead is ultimately a negligible difference. Emet taking the seat was the wiser choice and Hyth knew it. But yeah, still baffles me that people insist Emet didn't know who we once were (or hates us now. what? he's just a grump)... I mean... the game was pretty clear on that point, and he wouldn't have been nearly so disappointed were the opposite the case.

EDIT: I could have been clearer tbf, but I did mention I was low on sleep, so chalk it up to that.