Kogarah Golf Club owns less than half of its current site and has insecure tenure over the remainder. Almost all of that remainder is owned by Rockdale (now Bayside) Council and by NSW and various NSW government authorities. Almost all of the new site is owned by Rockdale (now Bayside) Council and the NSW Government.
With the new proposal, Kogarah Golf Club would have a 99 year lease (source: "Securing our Future"). That does not mean that the public will get the land back after 99 years. The lease on the Rockdale Council component of its current site expired in 1988 and the club is so far continuing to use it.
Here is a quote from "Securing our future": "These roads works have now brought the Club to a position where we have few options. Quite simply the Club cannot hope to maintain a viable membership on such a reduced course for the duration of WestConnex works." The club would obviously have an even smaller chance to survive if all public land were to be reclaimed. The outcome would be the sale of the club-owned land as is apparent from the document. As that land is not yet zoned residential (but only governments can rezone it), the NSW government would be in a position to buy the land relatively inexpensively, have it rezoned and resell it at a profit.
What does this all mean? If the NSW government insists on its residential development plans for the current site of the golf course, those plans can go ahead, even if the club does not move to the Southern Precinct. In other words, the development is not contingent on the alienation of public lands outside the current golf course site.
We have Rockdale (now Bayside) Council, various arms of the NSW government and the Boy Scouts. My understanding, and I don't have an authoritative source, is that the land that the Boy Scouts own is not where the developer is planning to put the golf course but on the eastern side of Muddy Creek where it would be impacted by the proposed bridge over Muddy Creek.
The diagram below is incorrect.