I believe what that refers to is the deletion of duplicate entries for the same song
I hope so...
Anyway, the Xbox Music experience IMHO brings a very bad light on the MS updates policies.
Xbox Music is an app, like many other apps, and most likely the fix for its issues is ready since a while, but we still have to wait with a phone where playing music is almost impossible, because it must be released together with an OS upgrade.
If they actually left some more access to the developer on the data on the microSD, by this time we would probably have a third party app to play music and another one doing wireless sync.
They didn't do that, so MS has to implement themselves all the fixes, and it is doing it with an extremely slow pace.
This is acceptable for new features, NOT for bug fixes of this entity.