So in other words, my interpretation is correct and the names are just in the wrong order. If you read it as it stands now, it says "There is no reason to use Dusknoir over Duskclops" which implies that Noir is weaker than Clops and should only be used in UU.
Anyway, the whole point of this was that when a Pokemon receives an evolution, it's prevoius form, even if still viable, falls off the charts. I'd say a good example from this past generation is Magneton, it was popular enough in Gen III OU, but now after Magnezone showed up, Magneton is rarely seen even in UU. Magneton is a particularly good example because it's higher speed is a real asset over its new evolution.
I realize that Magnezone is better in every other way, but that's not really the point. The point is that if a Pokemon is relatively powerful and sees some competitive use, and then gains a stronger evolution, the previous form seems to be completely forgotten even in lower tiers.