BH mass as a function of the dynamical mass for J2310+1855 (red star), compared with WISSH QSOs at z ∼ 2 − 4 (blue diamonds, from Bischetti et al. 2021), and luminous z ∼ 4 − 7 QSOs (green dots and violet squares, from Venemans et al. 2016, 2017; Willott et al. 2013, 2015, 2017; Kimball et al. 2015; Trakhtenbrot et al. 2017; Feruglio et al. 2018; Mortlock et al. 2011; De Rosa et al. 2014; Kashikawa et al. 2015; Neeleman et al. 2021). Jiang et al. (2011) used bulge masses, while all the other dynamical masses refer to the gas disk component. For J2310, the slope of the red arrow, with its uncertainty (shadowed red region), indicates how much the growth efficiency of the SMBH is slowing down with respect to the growth of the host galaxy.