Hmm... very interesting. Even then, we should ask why Chorae would burn rather than Salt a Cishaurim.
Chorae are products of the Aporos, which is to say language based sorcery where meaning is of crucial importance. Cishaurim don't die in quite the same way as sorcerers because the Psukhe isn't quite sorcery, but its so very close to sorcery that interaction with the Chorae produce similar but not identical effects.
As for Nannaferi, she seems to be a walking pinhole in the veil between the World and the Outside through which Yawter can pour some of her power. That might not be a terribly accurate metaphor because we don't have really bright and well educated characters giving detailed discourses on this subject, backed by millennia of scholarly works at this point in the series but since Mimara is a viewpoint character and she is likely to be around Akka, we may get this in the No-God. The book is scorched in the same manner as Nannaferi grows young, she receives premonitions of the future, and Meppa is healed. Yawter acts through her, changing the world without sorcery.