Point is to get the most surface area of the HS touching the CPU core. This being so, it doesn't matter if it is shiny as much as smooth, so even if the ridges are amazingly mirror finished, you still need to lap so that there are no ridges at all.
My SLK 900 had lots of ridges as well, and it only took a good 15 minutes of lapping to get rid of them, so I wasn't too dissapointed. I was going to lap it regardless of the finish, heh.