I just see the Aporos a school off Wards, but also all kinds pf anti-magic magic. They could have cants that paralyze, or somehow temporarily stop the subject from perceiving the onta. It doesn't seem too much of a contradiction in my mind. I think that just one facet of that school was the discovery of chroae, which is now the only artifact that shows us that it even existed. Like the Diamos is the forbbidden branch of Anagogic sorcery, perhaps chorae where a 'forbidden' magic of the Aporos. The production of chorae may have arisen from research into the Aporos, but that doesn't necessarily mean it follows the same mechanics as the rest of their school.
Follow that distinction, I wonder if one might classify the Diamos as a thaumaturgic practice... We don't "know" that summoning Ciphrang marks you or damns you (bit of a stretch).