I have to respectfully disagree with that.
If you are not a good caster and are slapping and slurping the water with your fly line and all your casts are landing harshly. Then it really doesn't matter how lightly the short furled leader is laying down because most all the fish in the area are going to be spooked away from your fly line slapping and slurping the water all over the place.

I have to respectfully disagree with that.
If that's the case it's not the fault of the leader thats spooking the fish, it's the caster!!