Thank you for your comment about CONSTRUCT.
SPARQL is defined to work with RDF and CONSTRUCT defined to create RDF graphs by receiving an HTTP-carried request and returning the results using one of the RDF concrete syntaxes. The SPARQL specification does not say anything about API use. It is not in the charter of the working group to define a new data framework going beyond RDF. SPARQL builds on the work of the RDF working group.
If an implementation wishes to go beyond the specification in some way, such as allowing API use to create other forms of triples, it is at liberty to do so, accepting responsibility for interoperability issues this raises. Interoperability is an important aspect for a web system.
The working group is not planning to make any changes in this area.
I would be grateful if you reply to this message to confirm that the working group has responded to your comment.
Yours, on behalf of the SPARQL Working Group,