Currently, you can set BOM Status in two different locations; within the part (which applies in every assembly in which the part is used), and in an assembly itself (via the feature tree right click menu), which obviously applies to only that assy.
As it stands, the only options available for BOM Status within an Assy are Normal and Reference. Whereas if you set the BOM Status at part level (or via the parent Assy BOM window), you have access to the full five options, Normal, Inseperable, Purchased, Reference and Phantom. Why can't the full range of options be specified at both locations?
As an example, you'll frequently set parts as Reference within an assembly, for a number of reasons. Perhaps they're called up somewhere else, are owned by a customer etc; there's any number of uses. But what if you want to maintain the mass properties of that reference part, without it actually being called up in the BOM. Well, unless you're happy to set the part to a Phantom in All assembiles, you're stuffed. You can't.
If we added an assembly BOM option of phantom however, it would solve this problem.