This is correct. For context, when the 747 was being developed, simultaneously Boeing was developing the SST, Britain and France were developing Concorde, and

This is correct. For context, when the 747 was being developed, simultaneously Boeing was developing the SST, Britain and France were developing Concorde, and the Soviets had their own supersonic Tupolevs in development. Boeing was anticipating that supersonic aircraft would render the subsonic 747 obsolete for passengers overnight, so it was designed to be easily convertible to freight.