  Merging black holes (BH) are expected to produce remnants with large
dimensionless spin parameters ($a_{\rm spin} \sim 0.7$). However, gravitational
wave (GW) observations with LIGO/Virgo suggest that merging BH are consistent
with modestly positive but not high spin ($a_{\rm spin} \sim 0.2$), causing
tension with models suggesting that high mass mergers are produced by
hierarchical merger channels. Some BH also show evidence for strong in-plane
spin components. Here we point out that \emph{spin down} of BH due to eccentric
prograde post-merger orbits within the gas of an active galactic nucleus (AGN)
disk can yield BH with masses in the upper mass gap, but only modestly positive
$a_{\rm spin}$, and thus observations of BH with low spin \emph{do not} rule
out hierarchical models. We also point out that the fraction of BBH mergers
with significant in-plane spin components is a strong test of interactions
between disk binary black holes (BBH) and nuclear spheroid orbiters. Spin
magnitude and spin tilt constraints from LIGO/Virgo observations of BBH are an
excellent test of dynamics of black holes in AGN disks, disk properties and the
nuclear clusters interacting with AGN.
