I've seen what you're talking about on a friends S4. The bracket for the end of the cable sleeve holds the sleeve at a slight downward angle instead of horizontal, so the topside of the cable is rubbing against the edge of the sleeve. I'm not sure why they did it that way, I agree it seems like it would cause some wear on the cable. However, I'd be surprised if the lifespan of the clutch cable was decided by that particular detail. usually they shear at the lever right?