Even in the mobileye presentation lines are not very realistic (other than perspective corrected and blended).
Also, I do not see how texture or scenery would or should matter to an autonomous system therefore road with all the markings could be fully computer generated.
I think the lines were supposed to be faded to replicate Japan's deceleration lanes? Not sure. But environment does matter because you can overfit/under fit your model to scenes from the sim, creating behaviors that you dont want when you get into the real world.