I've seen finish loss on the rails of all my Sig Classic series pistols. Admittedly... I've not pushed any of my guns to super-high round counts... but I feel like finish loss on the rails is inevitable. And expected. And while I'm no engineer, I've come to think that rail finish and integrity of the metal are separate factors. I've literally seen flakes of anodizing fall off the underside of the rails on my 1988 P226. And I'm not really all that concerned. I feel like the rails would probably still serve their purpose, with very little finish on them. Especially when adequately lubricated.
My Smith 3rd gens also show a lot of finish loss on the rails. And it seems to manifest more quickly, than on Sigs. And the Smiths run just fine. I don't necessarily think aluminum needs a beautiful finish to function adequately.