In some areas of the documentation responses include the property geofence_config_id on jobcode objects. In some areas it does not include this property in the documentation.
Furthermore, Update Jobcode says "Other properties defined on a jobcode object may be passed in to the request with a new value in order to change it. If the value passed in is the same as it was previously, or if a particular property is not passed in at all, it will be ignored." However, if you pass a jobcode object with a geofence_config_id set, the API will return "417 Invalid param(s): geofence_config_id"