The article (which I'm sure you read) is not about IIHS testing. It's about NHTSA testing. Also, I believe that Tesla planned on tweaking the car for this IIHS issue.
NSTHA and IIHS have different ways of rating cars. The best would be to top the leaderboards for both agencies, but Model S being first place and Model X being second place ain't no easy task though. Tesla has since addressed the issue since that test, so whenever they have another Tesla to test, it will reflect in that score.
I'm wondering if anyone knows a link to the leaderboard that Tesla mentions that the S and the X are the top two vehicles
Numerous automobiles in "Luxury Cars" category have ratings higher than that of the Model S. This includes the following: BMW 5 Series, Audi A6, Hyundai Genesis, Volvo S90, Acura RLX.
Photo caption from your link. "The seat belt allowed far too much forward movement of the dummy to the extent that its head hit the steering wheel hard through the airbag."
I imagine this could be tweaked in future builds and corrected?
Small overlap front: http://www.iihs.org/frontend/iihs/ratings/images/api-rating-...
Moderate overlap front: http://www.iihs.org/frontend/iihs/ratings/images/api-rating-...
You can clearly see a difference where the structural integrity of the door area begins to fail.
Compare that to the BMW 5 series in small overlap front: http://www.iihs.org/frontend/iihs/ratings/images/api-rating-...
There doesn't appear to be any structural damage to the door area.