  Recent data on the nuclear modification of W and Z boson production measured
by the ATLAS collaboration in PbPb collisions at $\sqrt{s_{\rm nn}}=5.02$ TeV
show an enhancement in peripheral collisions, seemingly contradicting
predictions of the Glauber model. The data were previously explained by arguing
that the nucleon-nucleon cross section may be shadowed in nucleus-nucleus
collisions, and hence suppressed compared to the proton-proton cross section at
the same collision energy. This interpretation has quite significant
consequences for the understanding of heavy-ion data, in particular in the
context of the Glauber model. Instead, we provide an alternative explanation of
the data by assuming that there is a mild bias present in the centrality
determination of the measurement; on the size of the related systematic
uncertainty. Using this assumption, we show that the data is in agreement with
theoretical calculations using nuclear parton distribution functions. Finally,
we speculate that the centrality dependence of the W$^-$/W$^{+}$ ratio may
point to the relevance of a larger skin thickness of the Pb nucleus, which, if
present, would result in a few percent larger PbPb cross section than currently
accounted for in the Glauber model and may hence be the root of the centrality
bias.
