Documenting what is copyable between the domain and standalon xml files

In the EAP6-UX meeting it was discussed that a smart user should be able to take the standalone.xml file and copy contents from it into a domain/host.xml file. From some point in the domain/host.xml files onwards the formats were said to be the same, is this true, if it is/is not the uniqueness needs to be documented, or strategies need to be explained.