Upvoting example for Firebase security rules

upvote-security-rules.json

{
    "rules": {
        ".read": true,
        "articles": {
          "$article": {
            "title": {
              ".write": "auth != null",
              ".validate": "newData.isString() && newData.val() != ''"
            },
            "url": {
              ".write": "auth != null",
              ".validate": "newData.isString() && newData.val() != '' && newData.val().matches(/^http.*$/)"
            },
            "votes": {
              ".write": "root.child('users').child(auth.uid).child('votes').child($article).val() != true"
            },
            "user": {
              ".write": "auth != null"
            }
          }
        },
        "users": {
          "$user": {
            ".write": "auth != null && auth.uid === $user",
            "votes": {
              "$vote": {
                ".write": "!data.exists()"
              }
            }
          }
        }
    }
}

Won't this mean a user can only vote once, but when they vote they can change votes t whatever they want?