Chapter 6.3 (Organization of Building Blocks) contains the following sentence:
"Each Object or ObjectType representing a MachineryItem supporting the AddIns should have an Object of type
FolderType or a subtype with the BrowseName “MachineryBuildingBlocks” (using the Namespace of this
specification), referenced with HasComponent or a subtype."

Since the previous paragraph refers to companion specifications and vendor-specific information models, I believe that the quoted sentence should be expressed unmistakably with regard to the namespace.

My suggestion:
"Each Object or ObjectType representing a MachineryItem supporting the AddIns should have an Object of type
FolderType or a subtype with the BrowseName “MachineryBuildingBlocks” (using the Namespace of the OPC 40001-1), referenced with HasComponent or a subtype."

The clearer, the fewer misunderstandings