"cannot select a non-group-by field at group-level" not enforced on relationship fields #4953

{
  "errors": [
    {
      "message": "cannot select a non-group-by field at group-level. Field: title"
    }
  ],
  "data": null
}

{
  "data": {
    "Book": [
      {
        "author": {
          "name": "David Foster Wallace"
        },
        "genre": "Fiction"
      },
      {
        "author": {
          "name": "David Foster Wallace"
        },
        "genre": "Nonfiction"
      },
      {
        "author": {
          "name": "George Orwell"
        },
        "genre": "Memoir"
      }
    ]
  }
}