  Recent works have uncovered an excess signal in the parity-odd four-point
correlation function measured from the BOSS spectroscopic galaxy survey. If
physical in origin, this could indicate evidence for new parity-breaking
processes in the scalar sector, most likely from inflation. At heart, these
studies compare the observed four-point correlator to the distribution obtained
from parity-conserving mock galaxy surveys; if the simulations underestimate
the covariance of the data, noise fluctuations may be misinterpreted as a
signal. To test this, we reanalyse the BOSS CMASS + LOWZ parity-odd dataset
with the noise distribution modeled using the newly developed GLAM-Uchuu suite
of mocks. These comprise full N-body simulations that follow the evolution of
$2000^3$ dark matter particles in a $\Lambda$CDM universe, and represent a
significant upgrade compared to the formerly MultiDark-Patchy mocks, which were
based on an alternative (non N-body) gravity solver. We find no significant
evidence for parity-violation in the BOSS dataset (with a baseline detection
significance of $1.4\sigma$), suggesting that the former signal ($>3.5\sigma$
with our data cuts) could be caused by an underestimation of the covariance in
MultiDark-Patchy. The significant differences between results obtained with the
two sets of BOSS-calibrated galaxy catalogs showcases the heightened
sensitivity of beyond-two-point analyses to the treatment of non-linear effects
and indicates that previous constraints may suffer from large systematic
uncertainties.
