The RUBIES survey delivers the largest statistical sample yet of the ionization parameter U at 3<z<9, using O32 ratios from 434 JWST/NIRSpec galaxies modeled with Cloudy photoionization grids. This preprint (arXiv:2605.30410) shows U rising by a factor of ~4 from z=2 to z=6 even at fixed stellar mass and sSFR, while declining with mass and increasing with sSFR. Prior JWST studies offered only case-by-case line ratios; RUBIES supplies the first population-level constraint linking nebular conditions directly to reionization photon budgets and early feedback. Earlier linear O32-U calibrations underestimated model-driven scatter, here quantified at 0.3 dex systematic uncertainty. The work connects to Bouwens et al. (2022) reionization photon-counting analyses and the JADES survey's z>8 luminosity functions by demonstrating that harder spectra and elevated q in low-mass systems can close the ionizing-photon shortfall without invoking exotic top-heavy IMFs. Limitations include reliance on a single line ratio and the broad degeneracy among Cloudy grids; future multi-line Bayesian frameworks are flagged as necessary. The result reframes cosmic dawn as a phase where feedback and ionization co-evolve rapidly rather than incrementally.