I know dimpling is normal but I can say that I look at my TSPP from 2005 or Indy from 1993 vs. my newer Sterns (Maiden, Kiss) and there's not contest. Newer pins have much worse dimpling.
Why? No idea. Maybe it's the wood. Maybe the airballs. Maybe a combo. Large magnets like in AS and BM66 pit like hell too and that's not a wood issue.
Does it hurt anything? No. But it is pretty crappy for the cost of a new pin these days.