it looks like ArcGIS Living Atlas has ingested a portion of the monthly iNat AWS Open Data Set into one of their layers. at lower zoom levels, the layer does some hex binning to present data in a way sort of similar to the Craigslist example here. you could also probably query observation data from the layer, although since it’s based on the AWS Open Data Set, it has all the limitations of that dataset.
i don’t think this directly addresses the feature request, and i personally wouldn’t advocate for this kind of visualization over iNat’s current map visualizations, but i thought it was interesting, if only as a curisoity.