I have a Fish Tales that has what looks like ribbing. Good news is, other than the ribbed look when viewed at just the right angle, the playfield hasn't worn abnormally after 25 years.

Also have an LOTR with slight ribbing on the playfield, again, no abnormal wear.

Yep, I've seen enough games with ribbing to consider it within production tolerances. It will probably lower the value of a game to some collectors but I haven't seen a problem with unusual wear.

It would be interesting to see if there is a difference in wear on new games that have the ribbing versus those that don't.

If anything, I would think if the ribbing is due to more grain in the wood, it might help the clear adhere to the surface better.

What do you consider "top notch quality"? Is it realistic to expect zero variation in production? If some variation in production is normal, what is acceptable?

Manufacturers usually hold there suppliers to certain standards that for pinball probably includes some level of ribbing, dimpling and chipping, because you see these things on playfields from the big manufacturers.

Problem is, no where is it stated to what degree these defects become unacceptable. In their defense, it seems like it would be difficult to put a hard specification on these types of issues.

My first NIB experience was an early WOZ. It had some ribbing on the playfield and the top of the back edge of the lower cabinet was shredded, like from a dull saw blade. I didn't think these defects were bad enough for JJP to toss the playfield and cabinet out, so chalked it up to unfortunate but acceptable levels of production variation.

I learned that if those kinds of things bother me, better not to buy anything sight unseen in the future.

TL:dr
Some variations in playfield and overall game quality is normal. Don't buy sight unseen if you're concerned with imperfections.

Their playfields may be better. It may also be that they don't get as many airballs, have as many exposed wood edges, have balls being shot out of kickers, etc.

I'm not familiar enough with their games to make a comparison.

I don't think I stated my point very well, let me try again. I work in an industry where we make products and guarantee their performance.

We will charge one price to guarantee a product works from say 7 to 10. Most parts will work from 9 to 10 but a 7 will pop up sometimes, maybe even a batch of them. If a customer wants guaranteed performance from 9 to 10 they have to pay more. Sure, everyone wants to get a 9 or 10 and pay the price for a 7 but it's the luck of the draw.

To me, getting a game with ribbing is like getting a 7 to 8, depending on how bad it is.

Yes, these games cost a lot of money but if the current standard gets raised, someone has to eat the cost of the rejected playfields.

Do you think the manufacturer or the supplier wants to cut into their profit margins, unless someone stops buying?

I think LEs should come with flawless playfields. Of course that means better QC, storing separate stock and risking a supply shortage if they don't get enough yield to the higher standard to meet demand.

Nothing is free though and I expect they would try to pass these costs on to us. They could use it as a selling feature and the collector LE buyers might go for it.

I guess we just see things differently.

I maintain that if you look closely, you will be surprised at how many games have playfields with ribbing. The playfields I have with ribbing do not wear more than those without, so it hasn't been a problem other than cosmetic.

Asking a manufacturer to throw away all those playfields is asking for a rise in quality.

We agree , but what should the manufacturers do until that happens? I guess they could shut down all production.

Otherwise, for now it's the new normal, live with it, protect your machines accordingly (chipping) or stop buying until they figure it out. Just my opinions, of course.

My early run WOZ (August 2013), LOTR and Fishtales all have this. No unusual wear patterns otherwise.

A little gentle ribbing never hurt anyone.

Well, if you consider just the 18 pins I have in the modern era (post 1990), 3/18 would be about 16%. Though not typical or desirable I wouldn't say it's exactly rare. If you look closely, I bet you'll see it on more games than you think.