You logic is flawed. A building is a structure but a structure is not necessarily a building.
That's not an issue with the logic. That's an issue with the definitions (which are too simplistic in art 100 apparently).
And my reading of the "building" definition would be that there are two classes of structures indicated: standalone and compound. Is there a third class I have not considered, a structure that neither stands alone nor is conjoined with other structures? It seems to me that standalone/compound would include all structures, definitionally per article 100.
Reverse the definitions (as you have), where all buildings are structures but not all structures are buildings, and it still indicates then that when either type is present you should have a disconnect.
If all buildings are structures, why did they include "building" at all?
And why would I assume that just because a building is within another building (or structure within another structure) that only the most meta-level building/structure would be triggered by this text? It has no such indication that it's only to be triggered one time per structure/building-compound.
I may be wrong here, certainly, but it's not due to my reading of the text, rather simply that's not "the way it's done" in practice. The text then needs clarification.