Yes. But I couldn't find any other reference to it. If you go to the CASA site and look up the basic rules you will not find that flying over someone else's private property is verboten.I think they are refering to some one else's private property without the owners permission.
(BYW, that web page is 12 months old.) I would love some more recent information.
No mention of it here:-
Flying drones or model aircraft recreationally | Civil Aviation Safety Authority
Or here:-
Droneflyer | Recreational drone rules and regulation