As far as we know, the Psukhe is a form of sorcery, in effect allowing the Cishaurim to achieve similar effects as the Anagogic and Gnostic Schools, including 'walking the skies.' So, as far as damnation goes, it's part of their metaphysics that they aren't marked, just like any other use of the Psukhe.
However, you bring up an interesting point I've had some thoughts about. In TWP, when the Cishaurim is approaching Kellhus on the rooftop, he is described as kind of zig-zagging through the streets, with his toes pointed down. No mention of walking the sky like other sorcerers, and the description doesn't mention walking, striding, stepping, etc. Almost like he was actually flying, which is supposed to be impossible, as other sorceries allow them to only walk the echo of the earth in the sky. So, do Cishaurim actually fly?