I was surprised at the parenthetical remark. Advantages of imported graphics include:
They help modularize a publishing process so that a graphic artist can concentrate on drawings without needing to learn an other aspects of the publishing process (such as how to use FrameMaker) while a technical writer need not remember to import new graphics each time an update becomes available.
Furthermore, if the publishing organization or its customer requires a database of graphics, it is easy to access graphics from the database or to create a database from the imported graphics in the FrameMaker document.
A generated list of referenced graphics makes it easy to confirm that all required graphics are included in a document, that no graphic is unnecessarily used multiple times, and that all graphics are stored at the appropriate location.
Yes, updates to graphics need to be coordinated with the editing/updating process in general, but that is always the case. I make no claim that imported graphics are always the best approach, but they are in many situations.