Although the DLPNO errors do increase with system size for both the circumcoronene ([n]graphene) and perhydrocircumcoronene ([n]graphane) dimers, the effect is much larger for the former, up to 5 kcal/mol larger for n = 54 when loose-MP2 thresholds are employed. This may result from many-body dispersion screening effects that arise in the conjugated systems, or what Dobson calls "type B" nonadditivity, 108,109 although this effect is ordinarily considered not to be captured at the MP2 level. Alternatively, it might simply reflect the more delocalized molecular orbitals in graphene as compared to graphane, leading to larger errors in a localized-orbital implementation. Whatever the origin, these data suggest that systems with extensive conjugation may represent some of the most problematic cases for the DLPNO approximation, for which the use of tight PNO thresholds should be considered mandatory.