Source Fields in Elasticsearch Index are arrays

I'm not sure if this is a bug or not but I've installed and enabled both Elasticsearch Connector and Search API, successfully created a few indices.

My issue is that in the elasticsearch index the source fields are arrays as opposed to strings... e.g.:

_source": {
          "type": Array[1][
            "event"
          ],
          "field_end_date": Array[1][
            1519925400
          ],
          "description": Array[1][
            "This talk explores how the speculative worlds of contemporary U.S. superhero comics have addressed the problem of difference and human diversity through stories ab...
           ],

Is this the intended structure?