It's a political exercise - the Indonesian courts are trying to show that she is getting every advantage they can give her. They really want people to believe she has had a fair trial, so from her perspective they want this done in public - so if it turns out this evidence doesn't hold up, everyone can see that is the case.
Which will be kind of difficult if there is a divide between the societies on what 'fair' is.
This is the first time that someone has suggested a plausible explanation -- Bali is being used as a waypoint for intra-Australia smuggling. Australia and Indonesia should work together to get to the bottom of this, and if it turns out that Corby looks like an unwitting mule, then let her go.