The current IndexedEmbedded handling doesn't support prefixes in a syntax other than "<fieldname>.": it relies on each field being exactly one component in a dot-separated path, which is wrong.
Note: there are tests that should pass when this ticket is resolved, and that are currently disabled in the pom.xml of the Elasticsearch module. Those tests will be (or have been) outlined as part of HSEARCH-2390.
Also, some relevant tests are disabled using the ElasticsearchSupportInProgress category.