Consider test score distributions. Scores >= 1400 on the new SAT apparently place you in the top 4% of SAT test-takers (who represent only ~half of all PSAT test-takers). Most Ivy/peer students seem to have scores in this range, presumably with commensurate GPAs and class rank. So perhaps it’s reasonable to assume that a majority of students at many Ivy/peer schools ranked within the top ~2% of their HS classes. That would translate to many Vals/Sals at small to mid-sized high schools.
As long as a college request class rank information, I think one has to assume it’s an important factor. I wouldn’t leap to the conclusion that Val/Sal status is necessary (or sufficient) for unhooked students at any of these schools … but I do think that rank outside the T10% (maybe even outside T5% at some places) makes admission rather unlikely.