This is true. The AI in this game is fair.
If you slam the brakes on late, on better tires than them from 4 car-lengths back in the braking zone then don't be surprised if there's contact (I'd expect no less from even the cleanest racers online)
If however you brake a bit later than them and find yourself on their inside approaching the apex, they don't just cut you off as if they are on a path that cannot be deviated from. They give you room to take the corner at a realistic speed.
Their faults are, they brake in ridiculous places
Their apex speeds are too slow
Sometime they will try to drive through you from behind, resulting in a spin.
It's not the best AI
It's a long way from what we'd like, but it's better than GT4.