I am very familiar with Taurus springs. My 95, that I bought new, at 60000 miles broke a spring on the driver side front sending the coil into my brand new BF Goodrich's with less than 400 miles on them. My 2000 Taurus broke the spring same position as the 95. The only thing that saved me from an accident was the spring shields that were installed a month before as part of a recall. Contours and Mystiques shared the same spring problem as the Taurus
From studying the geometry it understandable that spring sag would cause camber to be off. Yet, at such low mileage and across so many years of manufacture, that doesn't explain, when I have talked to multiple guys at different tire shops, why it is the right rear tire that is always cupped and worn the worst. (My brand new 90 LX wore tires evenly all the way around; no cupping at all in the rear.) The only thing I can see left is out of square spot-weld fixturing on the right rear that was done at the factory. It was laziness on Ford's part to use suspension adjustment as the fix for suspension location points that are off. I would think the target here is to be dead square with the way the car consumes tires most efficiently and to leave any minute error left to adjusters.