No, this isn't a joke. I just discovered that when you try to add an Esri JSON file as a new hosted feature layer, ArcGIS Enterprise throws an error and demands GeoJSON.
While GeoJSON is a perfectly great transfer format for spatial data, Esri JSON contains full schema information for replicating a layer - datatypes and so forth. Whereas in GeoJSON you lose all that.
Esri, I can't believe I'm asking you to please support your own format, but can we make this happen?
