Official Asus site: http://www.asus.com/Monitors_Projectors/VG248QE/
Where does it say G-Sync?
Also from that site:
The VG248QE is compatible with the NVIDIA 3D Vision® 2 kit**. Through NVIDIA® 3D Vision™ 2 glasses technology, it instantly takes you into another dimension - transforming all your gaming experiences and movies to 3D. Also with the latest NVIDIA® 3D LightBoost™ Technology, user can enjoy twice the brightness of conventional 3D technology in 3D mode with zero increase in total energy consumption.
** User needs to purchase the additional NVIDIA 3D Vision® 2 Kit for immersive 3D enjoyment.
Did you buy the G-Sync kit?