As a developer I would expect that embedding content within the RichText area would result in the embedded items available as relations of type "embed". Currently this does not seem to be the case.
1. Install eZ Platform
2. Embed an image to a rich text field
3. Navigate to "Related content" tab
4. Expect to see image listed as a relation, but it's not
To verify this is not an issue with REST/UI only, you can load the relations using the API. See attached image and code below