Let me try to jump on this roller coaster ride.
First, I don't enter chords from xml, so perhaps I am not really getting the point here. But assuming we are talking about midi play of the chord chart, BIAB will interpret what chords you enter and play something different each time you hit play. That is the way the program works - auto accompaniment generation not midi playback. So you really don't have any easy control over voicing of a chord or whether or not BIAB plays a third against your A2 or Asus2 or A9. In addition to that, BIAB is not a notation program where the chord chart is explicit to the playback. The chords drive the accompaniment engine. This is all. So I think you guys are over analyzing this whole thing. But that may just be me. So carry on.
Edit: Apparently Bob was typing as I was. I think we said the same thing, although he may have said it better.
Dan