Mods CAN'T HAVE real physics unless modder have access to real-life data from drivers or team, so at least only 1%, the others are completely random-closer-value but for sure not real 100%.
In order to be sell, AC needs at that time, to be better over rFactor which was extremely good on physics but not good on graphics. That was the fortune of AC.
Real car in game can't be handled by most of the casual sim-racer, that's why people loved so much AC because it was simulating, but also affordable and playable