false = the override was a no-op (already at the target / already terminal).
OptionaldefinitionAbsent only when the definition predates content fingerprinting.
The instance document _id — the per-instance join key (engine-minted
<tag>.wf-instance.<random>; caller-supplied ids ride verbatim). One of
the payload policy's two deliberate customer-string exceptions — see the
module doc.
Outcome flag for the admin-override events — the attempt emits either way.