Rear Suspension problems of the 2006 Toyota Sienna

The vehicle has rear alignment issues. The camber which are set at a negative value from factory caused an excessive wear on the interior outer lining of my run-flat tires. While on a family trip, the tire exploded on the interior side in traffic. Taking the vehicle to the Toyota dealer for new tires and inspection right after the incident, they returned my car with the new rear tire stating it is in need of a proper rear alignment. Upon research and taking my vehicle to numerous local tire shop/garage for opinion, they told me that the rear wheels cannot be adjusted or aligned due to the way it was built. However, Toyota insisted that the rear wheels can be aligned, so we did allow them to do a 4-wheel alignment. After receiving my vehicle back,it can be recognize that the rear tires are definitely not "straight" at all, by observation the bottom of the wheel is leaning toward the car. My concern regarding this issue is that many people with 4-wheels drive Sienna have the same problem with their rear wheel alignment. If this is an issue that Toyota do not fix, wouldn't that mean that we or any 4-wheels drive Sienna owners are prone to more accidents and must keep getting new rear tires?.