Possibly for E-mount lenses. I only have experience with the Sony/Zeiss lenses for the A-mount and their quality control was similar to their competitors.At the price point that the Sony/Zeiss lenses were marketed their QC vs. decent competition was outside the window.
That is also possible, sloppy manufacturing happens.You would also, maybe, be surprised at the QC variations that I have experienced with lenses costing up to 7 times the $1000.00 retail of Sony/Zeiss.
All I can say is that I used Hasselblad HC lenses and the ones I have are extremely well within specs.
I would not say that. And one should not forget that quality control of lenses is relatively straightforward: just put the lens on an optical bench. Quality control of, say, a car engine is comparatively complex for example.That being said, I think that lens manufacturing is a very difficult process with extremely difficult repeat-ability.