...there is a difference! Heat treating(aka tempering) is a process by which a bow's belly wood is heated to a charred surface to increase and improve the compression properties of that wood.
When you heat the bow wood to bend or straighten it you only want enough heat to plasticize the wood so it can be manipulated.
When I use heat to manipulate wood I usually use oil on the wood to prevent scorching. This allows me to make the change without drying out the wood too much. Steaming also does this. When I temper a bows belly I want to scorch the wood, solidifying the resins and cell walls to make that wood more compression strong.
It seem to me that some folks are interchanging or at least not understanding what these terms mean.