Got it back from Ruger today. In addition to "repairing" the grip frame, they replaced the mainspring housing assembly, sear spring, and slide.
Here are pictures of the left side of the frame where I had found the pitting. You can still see the pits, but clearly it has been refinished in some fashion to remove the oxidized material. Hopefully it was also passivated again to prevent recurrence.
I certainly plan to add removal of the grips for cleaning and oiling into my regular cleaning regimen.
View attachment 121922
View attachment 121923