They're an official code share airline within specific markets but they apparently are not part of the DM program. I suspect it is because of *A - they tend to restrict who you can earn miles with. HP's agreement with HA, VS, RJ & GQ are an exception but I suspect that those agreements were contractual and thus couldn't be eliminated since they were with pre-merger HP. WM's agreement was pre-merger with US and thus the *A rules apply. I suspect that once the contractual agreement with HA, VS, RJ & GQ are over, you'll see them dropped as well (as we've seen with BA and NW).