The Phantom Is in the Prior: The Two Headline Features of a Horndeski Hubble-Tension Model, Priced Separately

Prices the two headline features of the Horndeski Hubble-tension model of Tiwari et al. (2301.09382) separately: the phantom behaviour is guaranteed by the MCMC prior (phantom threshold c1 = 0.5, prior floor c1 = 2, quintessence point outside all priors), and the negative-density sign switch follows c3 alone -- z = 2.32 for the BAO fit (control: the target's printed z~2-5 window and Lya point at 2.34) but z >= 9.7 under the combined fit, whose c3 bound is 30.7x below the BAO value; the high-z negative fraction is exactly -4*c3 (-6.86% BAO, at most -0.22% combined).