已经配置了服务器地址URL接收用户事件消息，收到两个用户关注公众号的消息内容如下：

{"CreateTime":"1629270670","EventKey":"","Event":"subscribe","ToUserName":"gh_5ce61dc576d2","FromUseh-MDt4jZBNnUTxAYwuhlldFXf4A","MsgType":"event"}

{"Ticket":"gQGk8DwAAAAAAAAAAS5odHRwOi8vd2VpeGluLnFxLmNvbS9xLzAySEVKa1Z4N3o4M1QxMDAwME0wN3UAAgQeWhJhAwQAAAAA","CreateTime":"1629270674","EventKey":"qrscene_6","Event":"subscribe","ToUserName":"gh_5ce61dc576d2","FromUserName":"oh-MDt3TyHa7JSmmfqKgl3oD9Nfk","MsgType":"event"}

问题：为什么都是用户关注消息（Event：subscribe），消息体内容EventKey一个有值一个却为空呢？