I agree we should probably wait for official confirmation and that you can't explain everything away by saying it's an EV. Tesla is under a time crunch to get the car out and it sounds like they've hit the ball out of the park in all major categories other than the interior cup holder/storage/vanity mirror section. We could ask Tesla to burn through another few million in development costs to revise the interior but at this point we may have to move forward. Once the production car is actually out and people have lived with it for awhile then we can see what truly needs to change. For some, lack of a vanity mirror light or rear seat cup holders is a deal breaker and the Model S in its first iteration might not be the car for them. Tesla will have time to further work on the Model S down the road and refine the interior but if they stop now to tweak every little thing that each car must have because a cheaper car has it then they won't deliver any cars and Tesla will struggle.
If it's true, I don't think it would be a big deal for most people but that's just a guess (even if it is a basic feature on cheaper cars). Even a $100,000 S class Mercedes can't start up to warm the car in winter with the garage door closed. I find that a much more useful feature that vanity mirror lights but everyone has different wants and priorities.