Quoted from vireland:
Welcome to pinball!
Pitting (aka dimpling) is normal. It's most noticeable on a new playfield, but once there's a lot of dimples, it evens out and looks fine. Totally normal.
This is an urban myth that stern started to tell people. I believed it on my Star Trk. I have owned two a premium in 2014 thinking they fixed it but it looked just like my LE did. I have seen it on all sterns since then along with the insert issues. Dimpling never goes away or evens out. None of the old games have it. The MMR le, hobbit or woz have it. Stern is using softer wood. The grain is wider suggesting more fertizlers. My GBLE you can see the grain of the wood through the paint. It came that way. Almost looks like planking. Something is going on but don't think it evens out it just looks like the moon more everyday. I am not sure who is supplying playfeilds now to them or if they are doing in house. Many rumors. I was hoping on batman 66 they fixed this.