Leitz products all have to meet the same quality controls, so whether made in Germany,Japan or even Portugal and Canada, they all pass the same criteria.
Workers in various countries are only as good as their company lets them be and pays the cost of...during the years when US car makers like Chrysler were making crap the workers got the blame, but they pointed out that workers don’t set the assembly line speed, design the parts or set the tolerances.
I can’t tell any quality differences in any of my Leica products.