无法鉴黄 《内容安全》 security.mediaCheckAsync isrisky始终返回0？

请求：
curl -d '{ "media_url":"image","media_type":2 }' 'https://api.weixin.qq.com/wxa/media_check_async?access_token=token'

请求结果：
{"errcode":0,"errmsg":"ok","trace_id":"4f64315a2a46bc6f080d5743acadf615"}

返回结果：
{"ToUserName":"gh_95942377224d","FromUserName":"oUEE-5YPGrTXcsjg-mTDRxplKT8Q","CreateTime":1587526062,"MsgType":"event","Event":"wxa_media_check","isrisky":0,"extra_info_json":"","appid":"wxdf11d45c381d5e8a","trace_id":"4f64315a2a46bc6f080d5743acadf615","status_code":0}