reasoning
Under the lab-leak hypothesis, a DEFUSE-style project plus a covered-up leak would involve many people (collaborators, lab staff, officials), each with some independent chance of revealing it; Stansifer models each such person as having at least a 50% chance to leak some information, so the total probability that no evidence at all emerged is small. He initially estimates this as a Bayes factor of ~1/64 favoring zoonosis, then conservatively dampens it to 1/10 (log-odds -2.3) for the final table. He treats the secret’s non-escape as an essential “step” of the lab-leak theory, analogous to (and offsetting) the zoonotic side’s missing intermediate host (which he rates neutral).
Verdict (step 6)
Reconstruction — Premises: (i) a lab-leak scenario of the relevant kind (DEFUSE-style project plus covered-up leak) involves many people who would know; (ii) each such person has ≥50% independent chance to reveal some evidence; (iii) under zoonosis there is no secret to keep. Load-bearing step: therefore P(zero evidence emerges | LL) is small while P(zero evidence | Z) ≈ 1, so the observed absence of any whistleblower/leak is a likelihood ratio favoring Z. Evaluation: conditional on the premises the step holds — it is the standard “absence of an event highly probable under H1 but certain-non-issue under H2 favors H2” move; the 1/64→1/10 conservative dampening is a within-step magnitude choice. The candidate defeater — that some lab-leak scenarios (accidental infection of one field researcher with a naturally collected virus) involve few knowers, so no-whistleblower carries little weight against them — is a challenge to premise (i)‘s scope (how much of the LL hypothesis space implies many knowers), not an undercutting defeater of the inference given the premise; it is priced when the factor’s strength is set in step 7. Direction valid. Approved, checked.