I think it sends the right message to clubs. It is time to start moving forward and aim for average crowds to be above 20,000 for every club. Unless you have a home ground that can cater for over 25,000 fans plus sufficient corporate facilities, a finals match should not be played at the venue.
These romantic thoughts of playing high quality finals matches at suburban grounds such is Kogarah, Leichhardt, Campbelltown, Penrith, Shark Park etc is just nonsense. If your team makes the finals, you should have a sufficiently sized fan base to attract more than 20,000 fans.
The NRL is effectively saying to clubs that if you want to play at your home ground, take the steps like Newcastle and Wollongong. After redevelopment, these two grounds will have capacity of 35,000 and 23,000 respectively. The suburban grounds will be redundant in the next 10 years unless they are redeveloped and capacity increased.