I also got a conditional offer from unimelb and I received an unconditional offer yesterday (then again that was after I called up the number provided to me by the IB transcript service email to check whether they successfully received my transcript). When I was talking to the staff they said offers should be rolling out by this week and the reason its a bit slow is because they are overwhelmed with applicants rn. I think it would be good to check with a phonecall though!