  Clustering studies in current photometric galaxy surveys focus solely on
auto-correlations, neglecting cross-correlations between redshift bins. We
evaluate the potential advantages and drawbacks of incorporating cross-bin
correlations in Fisher forecasts for the Dark Energy Survey (DES) and the
forthcoming Rubin Observatory Legacy Survey of Space and Time (LSST). Our
analysis considers the impact of including redshift space distortions (RSD) and
magnification in model predictions, as well as systematic uncertainties in
photometric redshift distributions (photo-$z$). While auto-correlations alone
suffer from a degeneracy between the amplitude of matter fluctuations
($\sigma_8$) and galaxy bias parameters, accounting for RSD and magnification
in cross-correlations helps break this degeneracy - although more weakly than
the degeneracy breaking expected from a combined analysis with other
observables. Incorporating cross-bin correlations does not significantly
increase sensitivity to photo-$z$ systematics, addressing previous concerns,
and self-calibrates photo-$z$ systematics, reducing errors on photo-$z$
nuisance parameters. We suggest that the benefits of including
cross-correlations in future photometric galaxy clustering analyses outweigh
the risks, but caution that careful evaluation is necessary as more realistic
pictures of surveys' precision and systematic error budgets develop.
