The best I can tell, in spite of the fine pictures, is that you are merely experiencing FINISH wear. These revolvers have a rather tender finish on them. I have seen unsightly nicks in the finish in a gun shop (new revolvers that have been handled just a bit).

I don't think you are going to be troubled by actual wear with a reasonable number of the "heavy hitters" in the revolver.

I shoot target Wad cutters out of my 642 as the "regular" practice ammo, reserving the Plus P's for carry use (just shoot enough of the Plus P's to keep my hand in regarding recoil).

I reload and cast my own bullets so can easily adjust the loads to my needs.

I look at alloy frame guns as "shoot a little and carry a lot" compared to my "range babies", the 625's and 686's, etc. Alloy frames are wonderful for carry guns but less so for a lot of shooting. They are often less than comfortable to shoot and while I do NOT expect my alloy guns to fail, I tend to "shoot a little and carry a lot" with them as I mentioned.

FWIW
Dale53