IIRC, there were earlier reports (1998 onwards) where Holden found there was a need to carefully monitor oil capacity because of oil surge under heavy acceleration/braking - because the sump has been reversed when compared with US LS1s. I am sure the Australian owners will confirm or amend what I have written.
I also want to say the oil pan is different......and I will. They needed to redesign the sump to fit our application. The engine must sit further forward/rearward in an F-body or Vette than it does in the GTO.