I have a 'rust textured' bore rifle that shoots real sweet.
This gun does not copper foul at all. It doesn't do too well with cast or paper patched bullets though, being a two-groove. I cut off that end bit of the barrel after fire-lapping to ensure there was no 'trumpeting' of the bore.
Point is, it takes a lot of corrosion and etching to damage a barrel. Apparently, texturing a bore reduces friction and copper fouling. It does seem to hold lube better.