Are you talking as in smooth like an Iridium blade compared with a Feather?? A little more forgiving perhaps???
To me it just feels smooth as in the way it glides and the fact that I don't feel a thing when I shave with it. As if I'm using my Gillette Sensor. As opposed to say a Merkur HD or Feather Portable which I found rough during the shave and the face felt roughed up after the shave. I think it's a combination of the finish and geometry (blade angle and gap) that make the Feather SS smooth.