Unexpected behavior for rdfmigrate with datatypes

When migrating REO2.4.2 to REO2.5, some unexpected behavior occurs:

- `additions = desired - actual` results in only the new triples. So far so good.
- `deletions = actual - desired` results in 200+ triples:
- `schema:color` for classes. This is expected, because we manually add them in the migration.
- `owl:inverseOf` for a few CIDOC properties. My guess is Protégé inferred these.
- `rdfs:comment` *without* `rdf:dataype=xsd.string` attributes.
- `skos:notation` *without* `rdf:dataype=xsd.string` attributes.

The last two are problematic. I can see how they are technically not the same triples, but I am unsure why they are **not** in `additions`, as they *are* in the REO2.5 graph.