Patrick Chase
That's right, all steels have elastic moduli of 29 +/- 1 Mpsi. This means that for a given geometry all steels will develop roughly the same external stresses at the same deflection.

Where steels differ is in their tensile and ultimate strengths, and also the difference between the two. A soft steel with low tensile strength will fail elastically at lower deflection, but it may fail by bending instead of breaking, which is advantageous in the specific test David described.