Right question. Bundle alone proves nothing — you're correct.

Two things make it non-trivial to fake:

The pipeline is public. You can read scripts/steward_audit.py before running anything. It's not a black box.

For materials claims — the expected value isn't in the bundle. Young's modulus for aluminium is ~70 GPa. Not my number. Physics. The verifier checks against that, not against something I provided.

ML and pipelines — provenance only, no physical grounding. Said so in known_faults.yaml :: SCOPE_001.