It is not as complicated (but no less important) than one might think. There is an inspection of every lens that Alpa receives from Schneider and from Rodenstock. The lenses are used to photograph real world subject and the results are then compared to reference files from lenses that Alpa maintains in their inventory. Anthony Festa and I participated in this testing during our recent visit to Alpa. What we saw from the conclusions was that several lenses did not appear to meet the reference lens quality and were designated as "go backs".
Compared to buying a stand alone (unmounted) Rodenstock or Schneider lens from a generic source, this process removes the occasional poor performer, which as some have noted and described above, can occur as a result of numerous variation factors. So if someone ordered a Rodenstock or Schneider lens generically, there is a possibility they could have received one of these lenses, and perhaps wondered why the results were good, but maybe missing a certain wow factor. Some likely don't even question it. Expectations and results certainly vary with individual photographers as much as lenses vary themselves, so I'm sure every day someone somewhere has purchased a lens that really isn't as good as it could be, but continues happily (perhaps blissfully unaware) using it.
So the process is not complicated when you get down to it, but a critically important step considering the amount of measuring and checking tolerances that goes into the lens mount, camera body, digital back mount by Alpa for the optimal complete solution.
Steve Hendrix
Capture Integration