The strong correlation between solution density and diffusion has important implications for the interpretation of past works studying transport in similar confined systems, in which there exists a range of approaches for choosing the packing/density of a slit pore. Some studies apply the piston-based equilibration approach used here or allow the confining wall to move freely (a zero pressure condition), 57 while others aim to match the overall density in the pore to experimental bulk density values. Other works allow the slit to fill in contact with a bulk solution reservoir, a strategy which is only computationally feasible using force field-based simulations. More broadly, questions related to properly packing nanoconfined slits and rigorously defining the pressure in these systems comprise an active and controversial area of research. We hypothesize that differences in slit packing across the literature may be responsible in part for the wide discrepancy of confined ion transport trends described in the Introduction.