Hierarchy missing in ttl output?

[larswik]

Is your feature request related to a problem? Please describe.
A rest call, e.g. https://identifier.buildingsmart.org/uri/buildingsmart/ifc/4.3/class/IfcWall with "Accept" : "application/json" returns the class hierarchy while "Accept : "text/turtle" does not. Is there a particular reason that the response doesn't return the same content regardless of format?

Describe the solution you'd like
It seems as if the Dictionary schema allows for a "ParentClassCode". Eventhough a "ParentClassURI" would have been more useful (similar to rdfs:subClassOf), could "ParentClassCode" be a part of the response for a class URI? This way, at least the class hierarchy would be accessible in a linked data setting.

Describe alternatives you've considered
My knowledge of the API is limited right nowl, but I guess that one alternative would be to use the API, but, a simple access through URI:s is preferrable.

Additional context
application/json:

test/turtle: