That chart is simply supposed to show the effect that less RAM than you need has on gameplay. BF2 takes up more than 1GB of memory, fire it up, set it on High settings and see for yourself. Even though 1GB of memory will experience less extreme drops in FPS, as long as the game is taking over 1GB, the drops WILL be there, and they WILL affect your gameplay.
BF2 is THE game that made it necessary for gamers to upgrade to 2GB.
BF2 is THE game that made it necessary for gamers to upgrade to 2GB.