  The initial conditions in heavy-ion collisions are calculated in many
different frameworks. The importance of nucleon position fluctuations within
the nucleus and sub-nucleon structure has been established when modeling
initial conditions for input to hydrodynamic calculations. However, there
remain outstanding puzzles regarding these initial conditions, including the
measurement of the near equivalence of the elliptical $v_{2}$ and triangular
$v_{3}$ flow coefficients in ultra-central 0-1% Pb+Pb collisions at the LHC.
Recently a calculation termed MAGMA incorporating gluonic hot spots via
two-point correlators in the Color Glass Condensate framework, and no nucleons,
provided a simultaneous match to these flow coefficients measured by the ATLAS
experiment, including in ultra-central 0-1% collisions. Our calculations reveal
that the MAGMA initial conditions do not describe the experimental data when
run through full hydrodynamic SONIC simulations or when the hot spots from one
nucleus resolve hot spots from the other nucleus, as predicted in the Color
Glass Condensate framework. We also explore alternative initial condition
calculations and discuss their implications.
