Unnecesary, perhaps. But he isn't incorrect. If you read the whole of the first post, btarunr said the card would likely be 320-bit, not 384. So the RAM amounts will be more like the 570, less like the 580.
The GTX570 has a 320 bit bus, and there are 2.5GB versions
The 13-sm GK110, if it has a 320 bit bus can easily have 5GB VRAM using chips with double the density compared to what was in the GTX570.