After the
Monarch Piper Chieftain disaster, in which the aircraft flew into the ground while circling at night, the Australian AIP was changed so that descending to a 400' visual terrain clearance at night was prohibited - all circling at night must be at the circling MDA, until a constant descent to the runway is commenced.
I've been away from Oz for a while, so don't have the reference.
1920 refers to
the Air Navigation Act of 1920. 
When I said "That statement is simply not correct." I was referring to the "Don't descend until on final." statement. Not very clear, I know.