I have a CouchDB database with the following documents.

{
  "total_rows": 5,
  "offset": 0,
  "rows": [
    {
      "id": "3f46717d80b9c6be8b06d87ce80006c5",
      "key": "one",
      "value": "Value 1"
    },
    {
      "id": "3f46717d80b9c6be8b06d87ce80015df",
      "key": "one",
      "value": "Value 2"
    },
    {
      "id": "3f46717d80b9c6be8b06d87ce80031e6",
      "key": "one",
      "value": "Value 3"
    },
    {
      "id": "3f46717d80b9c6be8b06d87ce8003deb",
      "key": "two",
      "value": "Value A"
    },
    {
      "id": "3f46717d80b9c6be8b06d87ce80056eb",
      "key": "two",
      "value": "Value B"
    }
  ]
}

And this view.

{
  "_id": "_design/design",
  "_rev": "3-c0efd39596cb5af84b1d33f07e1b1090",
  "views": {
    "new-view": {
      "reduce": "function (keys, values) {n  return values;n}",
      "map": "function (doc) {n  if (doc.group && doc.value)n    emit(doc.group, doc._id);n}"
    }
  },
  "language": "javascript"
}

I query the view with this URL to get a list grouped by key, with the document ID of each record with that key.

$ curl 'http://user:password@localhost:5984/scratch/_design/design/_view/new-view?group=true' | jq

This is the output.

{
  "rows": [
    {
      "key": "one",
      "value": [
        [
          "3f46717d80b9c6be8b06d87ce80015df",
          "3f46717d80b9c6be8b06d87ce80006c5"
        ],
        [
          "3f46717d80b9c6be8b06d87ce80031e6"
        ]
      ]
    },
    {
      "key": "two",
      "value": [
        [
          "3f46717d80b9c6be8b06d87ce80056eb",
          "3f46717d80b9c6be8b06d87ce8003deb"
        ]
      ]
    }
  ]
}

That looks pretty good, except that the value values seem to be arrays of strings or arrays of arrays of strings more or less arbitrarily. (In a different database, the two ID in one group were each in an array of one string each, and another group had all three of its IDs in a single array.) Is this expected or am I going about it wrong?