The reason why the Caravan flew little or almost no base leg is because SeaPlanes are excempt from flying the 500 metre final leg. This excemption was designed more for water operations so the pilot can get a better view of where he's landing, or perhaps if flying into a valley, etc, prior to landing. It wasn't really designed for landing at Bankstown... a little play on the rules if you ask me, but you didn't, so there you go.
Merry Christmas.