Core's currently at the 6th variant of its JORC reserves as progressively more pegmatites are discovered and additional drilling on some of those pegmatites increases their size. See Below.
While ESS's 11.2Mt @ 1.12% is smaller than what Core has reported since June 2020, the largest individual component (Cade at 8.2Mt) is larger than any single pegmatite that Core has currently discovered and reported. Core's still drilling so further updates will ultimately occur.
Core got their project going using 14.72Mt of reserves but at that stage the Resource was 7.36Mt across Grants, BP33, Carlton & Hang Gong. In terms of size, ESS's Cade compares well with what Core had at FID although Core had the advantage of DMS while ESS looks likely to be needing DMS plus Flotation which will have a higher capex cost - partly offset by less pre-strip costs than Core had.
It would be good if some of those ESS targets come up with lithium bearing intercepts but most are likely to be dusters.