Jim,
Can you elaborate more on the testing soils. I have often wondered about that. Of course soil varies by region. Also there are many factors I am not convinced were addressed, such as food spills, compacted soils, petroleum oils, organic oils (food grade).
From what I can see, it appears that a synthetic soil was uniformly applied to a carpet sample, then testing was conducted.
Maybe I need to clean more carpets, but in the one I have cleaned, I have not come across any with a synthetic soil.
I have also never found one that was uniformly soiled.