Neutron-lifetime vintages behind the 2025-26 standard-BBN helium predictions

Standard Big Bang nucleosynthesis papers published in 2025-26 quote the predicted primordial helium mass fraction to +/-0.0002 or better but do not use the same neutron lifetime (879.4 +/- 0.2, 879.4 +/- 0.6, 878.4 +/- 0.5 and 878.3 +/- 0.4 s). Propagated through the LBT scaling law Y_p proportional to tau_n^0.733, the 1.1 s spread shifts the predicted Y_p by 0.00023, equal to the quoted theory error. The effect is negligible for neutrino counting but means SBBN predictions cannot be compared across papers at the 1e-4 level without normalising the neutron-lifetime vintage. Every number is a verbatim quotation or a ledgered computation; the RelSpec Workbench project, the full-text extractions, the reading verdict file and its independent review are deposited with the preprint.