MenuLink field external always returns false

I've created a menu link entity with an external URL and inspected it when the external field is resolved:

The value is actually FALSE in the MenuLinkContent entity. So this seems to be a core bug.

As a workaround you can get the same information by accessing uri in the link field and checking the __typename of the URL, which will be ExternalUrl.

query {
  entityById(entityType: MENU, id: "test") {
    ... on Menu {
      links {
        link {
          content {
            ... on MenuLinkContentTest {
              label
              link {
                uri {
                  __typename
                }
              }
            }
          }
        }
      }
    }
  }
}

Available in the 1.0.0-beta5 release.