Regarding your question in the thread title...
In the old days, individual expertise and corporate knowledge were important in creating good lenses.
In the modern era, anybody with the will ($$$) to do so can produce lenses at the limit of technology.
All aspects of design and manufacture are under computer control.
The Zeiss will have sparkle & a mysterious color that even Leica can' match.
Lenses do have a slight color bias, due to the different anti-reflection coatings used by different companies.
That's why I standardize on one manufacturer for the lenses on each camera.
But the effect is very slight, only noticeable in certain situations. And there's nothing "mysterious" about it.
Sparkle, on the other hand...
If you want to bet the ranch on your ability to accurately identify the presence or absence thereof 10 out of 10 times...
I'll happily take possession of your ranch.
- Leigh