Unclear if assemblies are subject to conformance and how.

One could expect that Assemblies are also conformance targets (described in a normative part of the spec, in 2.1.) Why aren't these mentioned in the conformance clause? It is not clear that an Assembly qualifies as a "DocBook 5.1 document", as it is described as a set of independent document units. It also has its own schema. So it appears that two conformance clauses at least should be written: one for DocBook 5.1 documents as implementation targets, the other for Assemblies. These different types of conformance targets should be distinguished, and the conf clauses be more specific about what requirements they need to satisfy.
(see OASIS conformance guidelines at: https://www.oasis-open.org/committees/document.php?document_id=55011&wg_abbrev=tab )