When the code changed regarding where romex could be used, I viewed this the way iwire and others have expressed it, but I have since changed my mind. I think it hinges upon what the word "permitted" means. I think a building is permitted to be built once a permit for that construction has been issued. And the type of construction of which it is permitted to be built is the type that is listed on the permit. The designer specifies the type of construction to be used and the AHJ approves that type of construction based on whether or not it fits within the code rules. There are times when a designer specifies type II-B construction for example, with an eye toward future flexibility even though type V-B would have been permitted had he specified that. Maybe the designer wants to preserve the possibility of a future addition to the building, or the possibility of a different type of future tenant.
If an electrical contractor takes it upon himself to say that the building could have been permitted to be V-B construction and wires it in romex, he is taking away the future flexibility that the designer intended to preserve. So, in my mind the type of construction of which a building is permitted to be built is the type that has been agreed upon by the designer and the AHJ, through the permitting process, and listed on the permit.
If the electrical contractor would like to save cost by wiring the building in romex, the proper course is to propose this to the designer. If the designer agrees, a change is proposed to the AHJ for a change in construction type. If the AHJ finds that the proposed change in construction type fits within the code rules, the AHJ would then change the the permit to allow the construction type to be V-B for example.