Yeh, Golgotteroth ain't gunna be anarcane ground.
Would kind of ruin the Consults day if they couldn't do sorcery there. (Especially Shae and Aurang).
Like I say, a Chorae undoes the Mark as well as the effect of sorcery, perhaps the manufacture of Chorae kind of irons out the ability to make a Mark/use sorcery in that region. Like an anti-mark.
Enchantments are laid on objects (sorcery cannot create anything besides channeling energy, from what we know) - e.g. the artefacts they recover from Sauglish would become mundane if they touch Mimara's chorae. This indicates that Chorae are manufactured objects, that are then enchanted.
The Mark or stain of aporetic magic could 'logically' be inimical to normal sorcery, creating an area where sorcery just won't work rather than undoing it. This is born out by the fact that Chorae protect their holder from sorcery but must connect directly to a sorcerous object to dispel it.
Altrernately there might just be a hoard of chorae buried under Atrithau.