I found at least this old Bug Report: https://forum.inaturalist.org/t/gps-accuracy-not-captured-when-uploading-photos-taken-with-a-camera-with-a-built-in-gps/18861/23
But I think it should have been solved by now!? I regularly create observations on iNaturalist by uploading photos through the website, and both GPS coordinates and accuracy are correctly extracted from photo metadata (their tags, as reported by ‘ExifTool’, are GPSLatitude GPSLongitude and GPSHPositioningError).