I thought I recall reading in that same document that you can omit the discriminating details on an embedded document and Doctrine will automatically add a `_doctrine_document_class` node, to allow you to persist mixed documents that may not necessarily be part of the discriminator. In the documentation I saw this about [mixing document types](http://docs.doctrine-project.org/projects/doctrine-mongodb-odm/en/latest/reference/embedded-mapping.html#mixing-document-types). That was what I was attempting to illustrate here. I probably should have used two three embedded documents with one not among the discriminated.