That may be the case, but it doesn't explain why vehicles sold in Europe, most of which are on the LongLife regime and thus using 504/507 oils, are experiencing the same issues. Neither does it explain why other similar engines in the VW empire using 504/507 oils are not experiencing similar issues.
It's highly probable that this is mainly a manufacturing/quality issue and not so much to do with the oil itself.
Using a more viscous (thicker) oil would be akin to treating the symptom, not the problem.