I bet these were mostly caused by toproping rather than wet ropes. I've seen grooves like this on lots of desert climbs, mostly 1 pitch climbs. We need to be mindful of rap placements and be willing to belay at he top to avoid this type of destruction whenever possible.
Rob, there's really not a climb here. Behunin is a very popular canyoneering descent in Zion, so, those grooves are caused by rope pull after a rappel is all. Wet or dry ropes would do that, IMHO. Really hard to prevent on low angle rappels such as this.