I kind of get the feeling that we get left overs from the bigger RHD market (UK).
Tesla probably pre-made a number of trims based on previous stats, not made to orders as Tesla is confident all would be sold.
UK gets allocated first because of longer sea transport and bigger backlog orders.
If your order is of similar taste to the Brits, maybe like white LRs, then you will be left waiting until there is leftovers rolling out of factory gate.
My other guess of the allocation process is that it may have something to do with currency exchange, as all sales ultimately go back to US in USD. It probably makes sense to allocate more and cashing in when AUD is strong and vice versa???