Campagnolo's official claim for the LOS (Lateral Operating System) design of the Athena derailleur was to maintain a constant chain gap. They didn't even mention indexing in the literature for the Athena rear derailleur but LOS was obviously an attempt to improve indexed shifting performance. Their previous designs did not work well as indexed derailleurs and this was their one of their solutions. I say one because they used an entirely different approach with Chorus. At the time, it seemed that Campagnolo didn't have a firm grasp of indexing and was using the multi-pronged approach to see which one won favour with the public. They would eventually standardize on a Shimano clone.