I think this is because of the composite shape. A question: can a
composite shape have a position that is different than its center? I think
yes.
I do not think that using anything else besides center is a good idea.
There are many places (e.g. TRConstraint) that counts on the fact that
position is a center. Other option would be to always return topLeft
corner, however the most important part that it is always the same. If you
wouldn't know what the position refers to than you can hardly use it.
Peter