I think it's like a slider level, with enabling unrealistic aids ( also depends on how it is implemented ,- limiting/smoothing player input side or internal physics calculation side, ie reducing effects of the forces affecting the car like inertia, g force, heat, wear ) and disabling certain part of calculated simulation physics like damage so you can abuse the engine/drivetrain like maniac, you are effectively reducing the fidelity or accuracy level of the simulation. This applies to all simulation based games, another example Pcars3, the tire is simplified, damage disabled, drivetrain simplified so you can downshift from high to low gear in an instant over revving the engine-locking up the tires with no consequences, unrealistic braking distance, persistent driving assists, just to name a few from what I read here. There's also a chance that the physics rate calculation may also be reduced to reflect the simplified physics, saving CPU cycle. Pcars 1 and 2 have 600Hz physics rate which IMHO barely above minimum of 500Hz ( which is also the minimum IRL for reasonably accurate damper telemetry with acceptable tolerances of error ) 1000 or 2000Hz should be the standard for simulation games.