"i'm with you. there are complications that come from grain structure, both tightness and length, inclusion of impurities (such as undissolved carbon), carbide fracture, and the tempering of the hardened blade that can change things."

"hypothetically, two annealed blades of the same mythical super steel, say M420V, are heated to austenitic temperature. the iron forms a new lattice structure in which the carbon content becomes soluble and you now have a tight, uniform, rigid grain structure without impurities (not realistic). the pieces are quenched differently. piece F is given a fast quench, maintaining a very rigid structure in the martensite and then tempered repeatedly to achieve a hardness of 56HRC. piece S is quenched a little slower, without tempering and achieves the same hardness with a more relaxed grain (hypothetical!). it's slightly normalized rather than tempered. now we've got the same hardness from the same steel, but they're gonna behave differently. "