Sorry, our public h.s. doesn't provide Naviance. I think it's more of a private-prep school thing.
Maybe WashU was particularly interested in students from CA and the West in 2006, but the kids my S knows who applied and got in all fell on the high side, if not above, the 25-75 percentile SAT range and had good grades, solid ECs, strong recommendations, the works. Some of the accepted students he knows chose other colleges, including his GF, who went to MIT. A couple from his h.s. applied and were WL or rejected. As I recall, they did not have as high SATs or class rank as my S did. So sorry, no data points to add to your research project.
My S applied RD and was admitted despite his NMF status ( 2310 SAT) and 35 ACT and top 2 percent class rank. He was an admitted Regents Scholar at UCB and UCLA and was also admitted to Cornell CAS and Northwestern and chose to go to WashU because it offered him everything he wanted academically and he felt comfortable and relaxed there.
I don't think WashU's admission policies are any weirder or more unpredictable than a lot of the other top colleges that are also spreading out across the country to look for high-achieving students who will make a good "fit." Some of MIT's and Brown's decisions are pretty strange if you ask me.