I don't recall exactly, but I usually try to do enclosed areas as relations, eg the Fairfax walk carpark to the east has to be a relation as it's fully enclosed by the natural wood area. The other car parks to the west are also enclosed but with an accompanying grass area (yes, this then makes the relation tricky to edit later). 
How else could enclosed areas be mapped? 
I didn't do the Q Station resort grassed areas but the messy white boundary areas are the editor avoiding both shared nodes and relations. I would have done that with relations :) The water/pond and cemeteries around there should also be relations.
I haven't edited for a while so I may have the jargon and protocols mixed up.