Good point. I'm not sure where I read it, whether in game or not, but supposedly Rukkha was the only archon that did not fight Khaenri'ah in the war, so it might still be possible that the timelines match up. Supposedly she was fighting to save Irminsul while that was going on. Still not sure if that happened after the Deshret incident or was during it.
You know thematically it's not just coincidence that this whole chapter is about life cycles, growth, seeds, plants, withering, roots, Irminsul, memories, desertification, etc. I just don't know how they're going to put it together for the story because it could feasibly work any number of ways, and they can always do the anime "asspull at the last moment" thing too, where the true story comes out of nowhere. I don't think they'll do that though, so we likely have all of the "pieces" to put the story together already.
I wonder if Kusanali is an archon "Seed", and if that's unique to her because of Dendro, or if all archons are bound by similar rules. The archons have all been somewhat linked to Irminsul, but most of them weren't as obvious with it. It IS obvious though, that Irminsul is going to be endgame of the story, at least in how it relates to Teyvat and what Celestia is doing there to begin with. We might have true endgame be in Celestia itself which I believe to be a foreign spaceship or something of that nature, not native to Teyvat for sure.
Anyways, for the other archons and their relation to Irminsul, we have -
- Venti - Vanessa's tree in Windrise. Not shown to have the typical white roots, but it's a unique tree in both size, shape, and significance as Venti keeps going back to it, almost like he's using it as a power source or talking to memories through it. Dragonspine was obviously either a tree itself or a place where Irminsul grew, as it was targeted by a Celestia nail and we see the white roots in there.
- Zhongli - His old buddy Azhdaha has Irminsul growing out of his back, also seems to be sealed by roots of Irminsul in his domain. Chasm targeted by Celestia nail, we see the white roots there.
- Ei - Makoto's seed and the Sakura tree are both Irminsul, well technically the same thing because of time/reality fuckery. I'm suspecting that when we get to the "nail" area of Tsurumi island, we will see white roots. We can already see 3 giant dead Irminsul trees on the island (which people mistake for mountains/volcanoes for some reason), and this explains the whole fog/ghost bits as Irminsul collects and houses the "memories" or the dead of Teyvat.
Hopefully the conclusion of Kusanali's chapter gives us some more info on what's going on with Irminsul, why Celestia wants to stamp it out on a grand scale, and why the archons are then using/protecting it. We know we'll get an explanation of why Dottore is burning it, so I'm sure we'll move the plot forward at least a bit from here.