I would suggest a possible reason is because Rolex (using your example) is a very large scale, industrially produced product numbering in (allegedly) the low million mark, while Roger makes very few watches a year. So when you make so few watches and charge such a high price for them, the QC should be that much better (since you are dealing with, by comparison, just a handful of watches) and closer attention paid to the product, to ensure easily spotted flaws are corrected before they are delivered.
I think it's fair to say you won't really see such flaws in Greubel Forseys, Ferdinand Berthouds or Haldimanns.
Just my opinion.
kind regards, kkwn98