I can't find anything on Parks website suggesting fire is prohibited in those specific locations. After all, NP wouldn't go through the trouble of setting up 4 benches if fire was not allowed. On the contrary (if I read right), the website states (for D'Aguilar National Park): Where can I have a camp fire?
You can have camp fires in many of our camping areas, as long as you use the fireplaces, fire rings or existing fire locations.
Help us protect our national parks by bringing clean firewood and kindling from outside the park—all the wood within the park is protected and cannot be collected or used for fires.
If you go with the mouse on the fire symbol, a box will appear saying: "Campfires allowed". But then, I'm inclined to trust the words of the Ranger. Unless he was a fake ranger