Here's something to ponder:
Let's say a trainee pilot happens to have an ARN and a CASA Basic class 2 medical.
Let's say they have two identical LSA aircraft there, one RAAus, one VH.
Let's say the trainee's instructor is dual rated RAAus/GA
Let's say the training records are identical for RAAus or VH for that school.
Given that there is no such thing as a student licence any more, what would be stopping an RAAus trainee doing the odd flight - even solo - in a VH aircraft if all those ducks lined up nicely?