Multivalue field and facet query - unexpected results...

_mapping_index3.json

properties: {
    id: {
        type: string
    },
    name: {
        type: string
    },
    bought_together: {
        dynamic: true,
        properties: {
            id: {
                type: string
            },
            name: {
                type: string
            }
        }
    }
}

_mapping_index4.json

    dummy_index_4: {
        sale: {
            properties: {
                bought_together: {
                    type: nested
                    properties: {
                        id: {
                            type: string
                        }
                        name: {
                            type: string
                        }
                    }
                }
                id: {
                    type: string
                }
                name: {
                    type: string
                }
            }
        }
    }

document.json

{
    id: 6,
    name: Bread,
    bought_together: [
        {
            id: 7,
            name: Cheese
        },
        {
            id: 8,
            name: Eggs
        },
        {
            id: 8,
            name: Eggs
        },
        {
            id: 7,
            name: Cheese
        }
    ]
}

facetQuery.json

{
  "query": {
    "text": {
      "name": "BrEaD"
    }
  },
  "facets": {
    "tag": {
      "terms": {
        "field": "bought_together.name",
        "size": 10
      }
    }
  }
}

result.json

facets: {
    tag: {
        _type: terms,
        missing: 0,
        total: 2,
        other: 0,
        terms: [
            {
                term: eggs,
                count: 1
            },
            {
                term: cheese,
                count: 1
            }
        ]
    }
}