it looks like EPA’s ecoregions at Level IV (https://www.epa.gov/eco-research/ecoregion-download-files-state-region-9#pane-04) are more granular than even the Jepson subregions, though they might not match the Jepson manual exactly. Because the EPA L4 regions are smaller, putting a few of those out in iNat probably wouldn’t be bad if they would actually be useful to anyone.