Greg,
It varies from business to business on how the mBOM is managed.
In certain organizations they might want to have definitive access control and what information is allowed to be modified by the manufacturing organizations, eg : Make/Buy flag , in such cases you may have to create mBOM "duplicate with propagation" which will allow whole eBOM structure is created in Manufacturing view and allowing the manufacturing engineer to do those changes , which is a very common and best practice.
In certain cases, if the most of the manufacturing changes are limited to top level assembly and no restructuring is required, you may want to go with your option.
Thanks,
Raj