My guess is that Woodmizer is buying "cold-rolled" (also known as "hard-rolled") strip steel, and this is where the hardening of the body of the blade comes from. They then induction heat-treat the teeth to further harden them. The hard-rolled body would have a very good cycle life, and would take the repeated flexing of a band saw blade very well. The heat treated teeth would have very good wear characteristics, and you might be able to get away with a harder (and therefore more brittle) tooth, since the body of the blade could have different properties more suited to the continual flexing. You could heat treat the whole thing, but one of the problems of a martensitic structure is that it is very "notch sensitive" - a small nick or imperfection will grow and crack resulting in failure of the blade. Hard rolled steel is more tolerant of these imperfections.