Bob Hoeft at the University of Illinois used to provide a "Crop Usefulness Index" of different soil test analysis. Many people interpreted his index as the accuracy of a lab analysis for each nutrient. Instead, it was a rating on a 0-100 scale of the usefulness or ability of each nutrient analysis to predict a crop response to an application of said nutrient.

If I remember correctly, pH was rated at 90 or above, P & K were in the 75-85 range, and the micronutrients were almost all rated below 50. Whether this took into account inaccuracies within the lab and with the analysis itself, I do not know. It was interesting nonetheless.

I do think we get too hung up on the innaccuracy of the analysis. One thing I have learned is that there are no absolutes. A lab analysis is the best we have. Until something comes along that is better, we have to live with what we have - even though it's less than 100% accurate.