SP Discussion, page-678

Off market trades are still reported to the market, after the fact. Prior to selling any stock, insiders subject to escrow must inform the ASX, who publishes that information (Insider Buying and Selling). So it is “dumping” on the market in effect because the greater market can clearly see it is coming, and they can clearly see at what price block trades are executed at, and the market will take that into consideration in repricing the security in question.

This is allowed, because it contributes to maintaining an orderly market, and contributes to an undisrupted view of price discovery.