on locked attestation pages, for instance https://www.beat-eu.org/platform/attestations/1444752237/, will it be possible to add more information such as at the very latest the results (error rates, plots).

Indeed, locked attestation are supposed to be inserted in publications under review, so that a reviewer can click on the attestation link and verifies the claims/results of the paper. So it will makes sense that the page shows those results.