A May 2026 arXiv preprint by Samuel Schlegel and colleagues exposes a critical blind spot in optomechanical routes to witnessing quantum gravity. The work is a purely theoretical analysis with no experimental data or sample size. Using the Wigner-Weyl phase-space representation, the authors demonstrate that the Gaussian-state, second-order Newtonian-potential regime adopted by nearly all current proposals admits fully classical explanations for apparent gravitational entanglement. This regime was precisely the setting assumed in the influential 2017 Bose et al. proposal (arXiv:1707.06050) and subsequent experimental roadmaps. The preprint shows that genuine distinctions between classical and quantum gravity only appear once experimenters move to non-Gaussian states or retain higher-order gravitational terms—requirements that raise the bar for both state preparation and readout far beyond present capabilities. A related 2024 feasibility study (PRL 132, 203601) already flagged decoherence and control challenges; the new analysis adds that even perfect isolation would still leave classical Wigner negativity as a confounding signature. Because the paper remains a preprint, its conclusions have not yet undergone peer review. The deeper implication is that mainstream coverage has understated the experimental stringency, potentially postponing any decisive test of quantum gravity by a decade or more.