ZF certainly has poor QC issues, but at the end, all reps are luck of the draw. I have not yet had a flawless rep from any factory, from dust underneath the dial, to crowns that don't fully engage to parts that aren't exactly fitted correctly. That is the nature of the replica watch game unfortunately. You accept things a bit more than their genuine counterparts.
That being said, if you look that GF vs Gen, you'll see things they got wrong where ZF got correct. At the end, it's a subjective opinion to which "flaws" are more acceptable than others. Surely any factory if they wanted to could replicate a watch pretty much asthetically the same. These subtle differences retain the replica and genuine watch market.