Nope. I have several NNs with feathered shanks. Unless they have a double dose of the gene there will be less feathering, but once you start crossing feathered leg with feathered leg you lose that reduction.
I haven't noticed a reduction in leg feathering on the showgirl legs. But then their leg feathers are huge... did you notice a reduction on birds with shorter/smaller leg feathers? It will be hard to tell if the bird has reduced leg feathers directly due to NN or just the genetic combination of leg feathering it happens to have.