Fixing that test in some manner and recompiling psql seems like it should be the easiest way to produce a core-only test case.
Apparently not - since it (ExecQueryUsingCursor) literally wraps the query in a DECLARE CURSOR SQL Command which prohibits INSERT...
I suppose we'd have to write a psql equivalent of ExecQueryUsingPortal that iterates over via fetch to make this work...probably more than I'm willing to try.
