Is it the case Datahike employs db.type/ref because it does not offer Datomic equivalent “Entity interface”?
datahike (and datascript) support a similar entity model. refs are equally supported by datomic https://docs.datomic.com/schema/schema-reference.html#db-valuetype
you define something to be a ref in the schema, so it can be directly joined against in a query; otherwise you would have to explicitly join against entity id. so [?a :my/ref-attribute ?b] instead of [?a :my/non-ref-attributed-id ?b-id] [?b :db/id ?b-id]
thanks whilo
Reading here: https://docs.datomic.com/reference/entities.html