The only FOBUS I can attest to owning and using, is for my full size S&W 1911. It "clasps" it at the trigger guard, and is a Yaqui style not completely enveloping the barrel and frame.
It is the SS finish pistol, and after two years, shows no sign of wear to the pistol or holster. (I do not carry this pistol everyday in the swamps of S. Fl.), but have noticed no marks.
I would offer that a daily carry sidearm, in such a holster, with another type of finish, would inevitably show signs of "holster use as some leather, even Nydex holsters can produce. My P3AT in a Nemesis holster, does have slight wear marks on the slide, and is just a pocket holster.
But not SS...I do not own a SERPA, but think the results would be the same over time.
Are you concerned with the blemish? Or the function?