Answer
PLSQLAP_Document_API always requires a root document name, so it can't produce a bare top-level object directly — the workaround is a small post-processing step: parse the resulting JSON CLOB with Oracle's native JSON_ELEMENT_T/JSON_OBJECT_T APIs, confirm it has exactly one top-level key, and re-serialize just that key's inner value back to CLOB as your final JSON. That gives you the unwrapped structure you actually want without needing PLSQLAP_Document_API to support it directly.