Create a yum enabled build promotion profile, and set it up so that it makes it's repositories appear in a yum enabled group repository.
Promote a staging repository into the build promotion profile, then retrieve "repodata/repomd.xml" through the group repository. This works.
Now promote a second staging repository into the build promotion repository, and retrieve the "repodata/repomd.xml" through the group repository again. The "mergerepo" command is not run, and the group repository still has the old yum metadata.
I've verified this is still a problem in both 2.11.3 and 2.11.4.