Something wrong in mongo atlas search string facet

MongoDB Atlas Atlas Search
3

Hi, @amyjian.
It is difficult to directly deliver the results because the questionnaire expresses my example abstractly.
And I’m using it well by indexing the string facet.
However, characteristically, when facet in an index defined only as token, the aggregate figures were significantly less or missing.
For example,

{
  "$searchMeta": {
    "facet": {
      "operator": ... ,
      "facets": {
        "keywords": {"path": "keywords", "type": "string", "numBuckets": 100}
      }
    }
  }
}

Result

only token indexing
{
  "b": 1,
  "d": 1,
}

changed string facet indexing
{
  "a": 1,
  "b": 2,
  "c": 2,
  "d": 1,
  "e": 1,
}