Comment on 'a Slightly Oblate Dark Matter Halo Revealed by a Retrograde Precessing Galactic Disk Warp' by Huang Et Al

Huang et al. (2024) measured the derivative of the phase ϕ_w of the Galactic warp traced by classical Cepheids with respect to their age τ and interpreted it as the warp precession rate ω≡dϕ_w/dt=-dϕ_w/dτ. This interpretation is unfounded: young stars follow trajectories close to those of their parental gas and trace the instantaneous gas warp, not its shape at their time of birth: ϕ_w should hardly depend on Cepheid age. We show that the measured dϕ_w/dτ>0 is consistent with an omitted-variable bias from neglecting the natural twist dϕ_w/dR of the warp and the R-τ correlation for Cepheids (originating from the Galactic metallicity gradient and the Cepheid metallicity-age correlation).