Suppose the story had gone like this: Simplicio measures X, and does it so well that his measurement has a correlation of 0.6 with X. Salviati examines lots of pairs (X,Y) and finds that X and Y typically differ by about 0.1 times the s.d. of X. Then the result would have been the same as before. Would that be a reason to say "measurement is no good; use probability and statistics instead"? Of course not.

Indeed. What matters is not what the procedures are called, but how they compare. Salviati's results completely trump Simplicio's.