I think people are just having a fun time making fun of all the marketing hype found in the golf industry.
True, the vokeys are carbon steel, which is soft compared to other steels such as stainless. BUT... the wedges are cast of this material, not forged from it.
Heat treatment has effects on the hardness of the metals. I would assume the "Heat Treatment" is in concerns to the cooling rate of the casts, and the difference that the rate at which a metal cools affects its hardness. That is my guess at least....