Retractions in PubMed

For those who don't know, PubMed lists retractions (in addition to the standard stuff like articles, editorials, etc.).  The details regarding how PubMed decides when to flag retractions are provided here.

With retractions on the rise, I think PubMed retraction listings can play a useful role in helping hold authors accountable for publishing misleading formation.  For example, I hope NIH reviewers check PubMed to watch out for PIs with tainted records.

However, I noticed an inconsistency today that made me curious about how these retractions are annotated.

For example, take a look of these two Anil Potti papers that have been retracted:

This is how retractions should look:

However, this other paper doesn't have the retraction designation, even though there is already a separate PubMed entry for this paper's retraction::

There is a 2007 erratum mentioned for the New England Journal of Medicine paper but no retraction flag (as could be seen clearly for the Nature Medicine paper).

If anyone can provide additional information on this topic, then I would certainly appreciate it.