This!! Blaming the changing clearcoat technology is BS, car manufacturers and paint suppliers have been dealing with this for years, and today's clearcoat paints when formulated correctly are stronger and more durable than ever before. The key is using the right, i.e. the more expensive, formula of clearcoat.
The other thing that may be affecting this ghosting is the rest time of the inserts versus wood. If the playfield is painted too quickly after the inserts are set into the playfield the epoxy or whatever used to glue the inserts may not have time to set correctly.
Either way, if Stern wanted to seriously fix this ghosting issue it is well within their powers to do so....