I think you are right about the heat treatment. Heat treatment does not only influence hardness and with it the ability to hold an edge. It also has influence on the grain (achievable sharpness and stability) and potential internal cracks. Yet few people talk about the quality of the manufacturers heat treatment.
Puma knives used to come with a mark from the HRC test and a sticker pointing at the mark. Puma used that to demonstrate that they did a 100% test for their heat treatment.