The only thing I have read, that makes sense, is Brunswick outsourced the 3's and they had no quality control. Included in that rumor, Brunswick was unhappy with the quality and started to produce them again. I don't really know if that is true, though...
There is also an issue about slate pins...
IMO, there should be no problem with any Gold Crown as long as the geometry is there. Level the slates, stretch the cloth even, and square the rails and it will play perfect (asuming cushions and cloth are good)
I have a GC1 from 1962. It plays just as good as any other GC (set up correctly) including several GC3's.