Record the workflow, not only the final output
For regulated or high-impact use cases, the useful evidence may include the source material, model version, prompt or configuration, generated draft, reviewer decision, and published version. Timestamping hashes at these milestones can show which artefact existed at review time without storing sensitive source content with the trust service.
What a timestamp can and cannot prove
A timestamp proves that a particular digital representation existed no later than the trusted time and that it has not changed since issuance. It does not prove that the content is true, that a model was fair, or that a reviewer made the right decision. Pair it with access controls, provenance metadata, and a documented review policy for a defensible governance record.