Originally Posted by
FBinNY
Those are "scroll marks" left by the point of the cutting tool as it spirals in (or out) when the rim is machined. You see the same on many lathe turned objects, and they're incidental to the process. There's very little depth so it's not relevant when they smooth out. If the rim has just become smooth, you've probably only seen less than 10% or so of the service life worn off.
It's actually a deliberate finish.
Rims can be used as extruded and anodized but the brake wear will be ugly and uneven until all the anodizing wears through. They're smoother as-extruded than after machining. Only the lowest-end machined aluminum components have such a rough finish left on them incidentally. At the price of most non-entry-level wheelsets they could surely spec a finer finish if they wanted.