This is because there is only one CAD file for all the items in the family table. It's a sort of fiction that there are any other parts. The problem of control is that PTC doesn't have a way to tell if changes made to the one CAD file affect all the fictional parts or not. In a way it is more like a copy of a specification, where adding additional items revises the specification, including all existing items covered by the spec.
Even so, I thought one could request that only the generic and a subset of instances be subject to revision.
An alternative is to use inheritance where there is a primary part from which others are derived. This would allow multiple children parts, each with their own revision scheme. OTOH, if a change is made to the primary part there is no guarantee the children parts will be correctly revised.
Clik here to view.
