New Shoutouts API and EventSub subscription types are now in open beta

Announcements
3

The docs for ‘channel.shoutout.create’ and ‘channel.shoutout.receive’ EventSub subscriptions note ‘broadcaster_user_id’ as optional and ‘moderator_user_id’ as required in the ‘condition’, yet not setting the ‘broadcaster_user_id’ when trying to subscribe throws a validation error:

data {
  error: 'Bad Request',
  status: 400,
  message: "unknown validation error: Key: 'SubscriptionCondition.broadcaster_user_id' Error:Field validation for 'broadcaster_user_id' failed on the 'required' tag"
}
config {
  transitional: {
    silentJSONParsing: true,
    forcedJSONParsing: true,
    clarifyTimeoutError: false
  },
  adapter: [ 'xhr', 'http' ],
  transformRequest: [ [Function: transformRequest] ],
  transformResponse: [ [Function: transformResponse] ],
  timeout: 0,
  xsrfCookieName: 'XSRF-TOKEN',
  xsrfHeaderName: 'X-XSRF-TOKEN',
  maxContentLength: -1,
  maxBodyLength: -1,
  env: {
    FormData: [Function: FormData] {
      LINE_BREAK: '\r\n',
      DEFAULT_CONTENT_TYPE: 'application/octet-stream'
    },
    Blob: null
  },
  validateStatus: [Function: validateStatus],
  headers: AxiosHeaders {
    Accept: 'application/json, text/plain, */*',
    'Content-Type': 'application/json',
    Authorization: '<redacted>',
    'Client-Id': '<redacted>',
    'User-Agent': 'axios/1.2.2',
    'Content-Length': '175',
    'Accept-Encoding': 'gzip, compress, deflate, br'
  },
  method: 'post',
  url: 'https://api.twitch.tv/helix/eventsub/subscriptions',
  data: '{"type":"channel.shoutout.create","version":"beta","condition":{"moderator_user_id":"<redacted>"},"transport":{"method":"websocket","session_id":"<redacted>"}}'
}

The same happens if only providing the ‘broadcaster_user_id’.
It only works when providing both at the moment.