re-making bibo:identifer a subPropertyOf dcterms:identifier

Issue spotted by Jay:

I noticed that the definition of bibo:identifier has changed and is no
longer a subPropertyOf dcterms:identifier. Was this an error?

v1.3
###  http://purl.org/ontology/bibo/identifier
:identifier rdf:type owl:DatatypeProperty ;
            rdfs:range rdfs:Literal ;
            rdfs:domain [ rdf:type owl:Class ;
                          owl:unionOf ( :Collection
                                        :Document
                                      )
                        ] .

v1.2
###  http://purl.org/ontology/bibo/identifier
:identifier rdf:type owl:Class ,
                     owl:ObjectProperty ;
            rdfs:subPropertyOf terms:identifier ;
            owl:objectPropertyDomain :identifier .