John,
True enough I just think it is easier to do, but the danger that part attributes in the displayed part can be edited this way whereas any components will be assigned with object attributes rather than part attributes. On first explanation it is as hard to grasp as it is to explain. The functionality has its place but personally I would consider it an improvement if the dialog did allow you to edit the part attributes from the ANT if you have write access available to you..
Cheers
Hudson