Reasoning
G-M compute Bondi-type accretion rates from first-principles physics across the range of extra-dimensional gravity scenarios (varying the number of dimensions and warping, which set the black hole’s effective capture radius at subatomic scales). The scenarios split into two classes: (1) accretion so slow that Earth suffers no macroscopic effect within the Sun’s natural lifetime - no risk regardless of production; (2) accretion fast enough to matter. In class (2), the same short-distance gravity makes trapped black holes inside far denser white dwarfs and neutron stars accrete those bodies on timescales much shorter than 1 Gyr. Since cosmic rays guarantee production and trapping there (see the stopping-power argument), catalogued >=Gyr-old white dwarfs and old neutron stars would not exist. They do; therefore every class-(2) scenario is empirically excluded, and no scenario is both realizable and dangerous. Caveat load-bearing assumptions: the accretion modelling (contested by Plaga) and cosmic rays actually reaching WD surfaces (low-B WDs) carry the weight.
Verdict (step 6)
approved / checked. Reconstruction: exhaustive two-class bracket on Earth-accretion timescale. Class 1 (slower than macroscopic effect within solar lifetime) is harmless by definition — tautological, valid. Class 2: (P1) the same short-distance gravity that makes Earth accretion fast makes accretion inside far denser WD/NS much faster than 1 Gyr; (P2) cosmic rays guarantee production and trapping in WD/NS (A-1’s conclusion). Then observed >=Gyr-old WD/NS exclude every class-2 scenario. Conditional on P1-P2 the dichotomy is exhaustive and each horn closes, so the inference holds; no undercutting defeater — a scenario dangerous to Earth but slow in a denser body would deny P1 (premise truth, priced at step 8 where Plaga’s accretion-modelling challenge lives), not the inference. Traced the bracketing structure directly.