A lot of people bash the X2010 as an unrealistic car. However, I have zero doubt it could be built and perform exactly as it does in the game. It was designed by Adrian Newey who is considered by most to be the greatest car designer in the history of Formula One. He has multiple F1 championships to his credit, including the defending champion Red Bull team.
Even a modern F1 car with all the regulations and restrictions imposed on the design generates enough downforce to allow the capability of driving upside down (proven in many computer simulations). I see no reason why Newey's X2010, built purely for speed and grip, unfettered by regulations, could not be built. I consider it a real car, and though there is not much practical use for it other than grinding, it's a pretty fun car to drive.