Starting description, from comments in avmoverview.doc The VM uses this property when it copies traits from the base class to the current class for the purpose of building a single traits descriptor -- traits in the protected namespace of the base class are renamed to be traits in the protected namespace of the current class. As a consequence, it is only necessary for multinames to carry a single protected namespace entry. ASC generates massive multinames containing also the namespaces of the base class, but it’s not clear that that is actually necessary.

Tamarin isn't maintained anymore. WONTFIX remaining bugs.