I recently was shown photos of a X5 with third row that had been in a rear ender.

It was a friend who has been working in China for BMW that had taken shots of a X5 overthere that had been hit by a truck at lowish speed.

His point of taking this was to show that BMW have invested time into making the rear crumple zone a lot more rigid for the sake of third row seat option.

That being said I will only ever put one of my three children in the third row if they or we have friends wanting to travel with us as well. Not a spot I would put them in daily.

dont really care who has made the car the rear doesnt have that large thing called an engine attached to it which offers some impact absorption