Wilshire, it seems we have a defining quote: "The Gnosis is simply what the Anagogis could be if the proper conceptual leaps were made" - which states an evolutionary link between two magical paradigms. All we need to consider is a factor of a nonmen participation, a true reason of that short "if".
Maybe, nonmen tutelage was just a time-saver which gave halaroi a new branch of sorcery a few thousand years earlier. Maybe, nonman's cognition is truly alien and acts as an essential ingredient, so halaroi by itself are limited to the forms of anagogic sorcery and, if they are too lucky, they can comprehend and repeat some gnostic explanations of Gin'Yursis.
First variant states for Kellhus ability to reinvent Aporos on the fly, because he was clearly making scientific breakthroughs while just listening to Akka's teachings abouth common math, logic etc. Second variant states for a bridge where even Aspect Emperor shall not pass. No halaroi allowed, lol, even if they are tweaked ones!
As for myself the second options looks more real. Two thousand years passed but there is no big signs that "conceptual leaps" could be made through pure human efforts. And we're talking abouth Scarlet Spires here. About few-hundred-year-old-mageocracy with tremendous intellectual power, who knows the overall direction of research.
So I can only guess what halaroi lack to invent gnosis and/or aporos by themselves. After all, cunuroi were a long-living specie with a lifespan about 400 years even before the inchoroi. Maybe it's just a difficulty of culture transmission & accumulation? One mortal cunuroi philosopher is equal to a sequence of 5-10 mortal halaroi adepts of a certain philosophic school, who will have to study their predecessors reflections and to live under a constant chance of extinction even before making their first worthwhile discoveries. Cunuroi is just a better basket for knowledge. :c
A second thought. Do they use aporos to make anarcane grounds or it's a meta-aporetic level of intervention? The most famous anarcane is Athrithau, located on the far north and near Ishterebinth. A former cunuroi lab, abandoned after ban on the Aporos?
A third thought. They should have some apotetics or meta-aporetics nerds in Min-Uroikas for anarcane is the opposite of topos. And it's generally a bad idea to be horribly damned and at the same time to live right somethere, where curious ciphrangs can just pop out of the thin air and grab your ancient consulty ass.