opensearch _explain output blank (ElasticSearch)

I'm trying to work with cloudwatch log data in opensearch. While building some dashboards, I'm querying by "@log_stream". My log streams vary slightly, like "productName_filterlog" and "productName_messagelog". However, my query for one "@log_stream" yields results with many different log streams mixed in. I'm doing a term search with explain enabled in hopes of getting some reasoning for this:

Request

POST myindex/_search?explain=true
{
   "query":{
    "term": {
      "@log_stream": "productName_filterlog"
    }
  }
}

Response

...
"hits": [
   {
      ...,
       "_explanation" : {
          "value" : 1.0,
          "description" : "*:*",
          "details" : [ ]
        }
   }
]

My question : what does this _explanation object mean? Why is it so useless? Is there a better way to determine why some unwanted results are showing up? I'm assuming the reason is due to some analyzer shenanigans, but how would one determine this?

thanks!