Synthetic-persona providers label a minority of their population "human-grounded" to distinguish it from algorithmically sampled records. That label confirms a record traces to a real panellist's account — not that the person who supplied the answers matches the account's demographic profile. The market research industry already documents this failure as participant misrepresentation. Where the mismatched respondent is a minor, GDPR Article 8's parental-consent verification duty becomes unreachable by design.

Providers of general-purpose AI models with systemic risk must document adversarial testing and any involvement of independent external evaluators under Article 55 of the AI Act. Population-scale synthetic-persona simulation infrastructure is a plausible candidate for that role — external to the model provider, but not independent of itself when its own population and validation figures are self-reported. No such case has been identified; this article examines the structural gap that would arise if one did.

A market has formed around cryptographic certification of synthetic datasets — SHA-256 fingerprints, Ed25519 signatures, publicly verifiable registries. The better providers state plainly what this proves: integrity and authenticity of the certificate, not generation quality. That honesty does not close the gap that matters under Article 10 of the AI Act, especially where the same platform both generates the data and signs its own certificate.

Synthetic-respondent platforms now screen advertising claims before launch, reporting their own alignment rates against real consumers. EU and UK advertising law already require that the evidence behind a claim be adequate and independently defensible. A validation figure produced solely by the party selling the testing infrastructure does not meet that standard — it is the claim requiring substantiation, offered as its own substantiation.

An AI evaluation infrastructure built on billions of synthetic persona records reports a high adherence rate — proof the model can play an assigned role. Article 10 of the AI Act asks whether the declared population is representative of real users, and who, independent of the producer, can confirm it. This article examines the gap between the two.