Field boost changes in ElasticSearch version7.6.2

We recently moved to ElasticSearch version 7.6.2 from version 6.2.3
The search query that we use has field boosts applied in different match queries. I was looking into the changes related to scoring of docs in the new version and found that the boost applied in the newer version varies from the actual number that I used in the search query.
(I checked using the explain API).
eg.,
Search Query:

{
  "explain": true, 
  "query": {
    "match": {
      "connectorSpecific.alpha": {
        "query":"goexpense",
      "boost": 5
      }
    }
  }
}

Score Generated:


        "_explanation" : {
          "value" : 46.694355,
          "description" : "weight(connectorSpecific.alpha:goexpense in 226) [PerFieldSimilarity], result of:",
          "details" : [
            {
              "value" : 46.694355,
              "description" : "score(freq=1.0), computed as boost * idf * tf from:",
              "details" : [
                {
                  "value" : 11.0,
                  "description" : "boost",
                  "details" : [ ]
                },
                {
                  "value" : 6.449522,
                  "description" : "idf, computed as log(1 + (N - n + 0.5) / (n + 0.5)) from:",
                  "details" : [
                    {
                      "value" : 2,
                      "description" : "n, number of documents containing term",
                      "details" : [ ]
                    },
                    {
                      "value" : 1580,
                      "description" : "N, total number of documents with field",
                      "details" : [ ]
                    }
                  ]
                },
                {
                  "value" : 0.6581793,
                  "description" : "tf, computed as freq / (freq + k1 * (1 - b + b * dl / avgdl)) from:",
                  "details" : [
                    {
                      "value" : 1.0,
                      "description" : "freq, occurrences of term within document",
                      "details" : [ ]
                    },
                    {
                      "value" : 1.2,
                      "description" : "k1, term saturation parameter",
                      "details" : [ ]
                    },
                    {
                      "value" : 0.75,
                      "description" : "b, length normalization parameter",
                      "details" : [ ]
                    },
                    {
                      "value" : 1.0,
                      "description" : "dl, length of field",
                      "details" : [ ]
                    },
                    {
                      "value" : 4.1031647,
                      "description" : "avgdl, average length of field",
                      "details" : [ ]
                    }
                  ]
                }
              ]
            }
          ]
        }

Is there a reason for such a difference in boost?