Storing data in empty Array returns empty Array (only in AppScript)

I wrote a simple iterator to loop trough a JSON object and parse the object into a new form. This works as expected in almost any JS environment. (For example in the console( However, the function below returns an empty array when executed in AppScript.

returns : [[], [], [], [], []]

This problem seems to be AppScript specific. Before I submit a bug through Google Developer Group I like to understand if this might be an App Script specific and intended behavior.

function parseBQData(/*tableData, request*/) {
  var tableData = [["20220301","(none)","(direct)","3","1","1"],["20220301","organic","google","3","1","1"],["20220302","(none)","(direct)","4","2","2"],["20220302","organic","bing","1","1","1"],["20220303","(none)","(direct)","1","1","1"]]
  try {
    
    // store the array of dimensions and metrics in a variable called 'fields'
    var fields = ["date", "medium", "source", "pageviews", "sessions", "users"]
    
    // create a new empty array to store the parsed data
    var newtableData = new Array();
    
    // loop through each row in the tableData
    for (var i = 0; i < tableData.length; i++) {
      
      Logger.log(tableData[i]) // This returns: [20220301, (none), (direct), 3, 1, 1], [2022]


      // create a new empty array to store the current row
      var wrapper = new Array();
      
      // loop through each column in the row
      for (var j = 0; j < fields.length; j++) {
        wrapper[fields[j]] = tableData[i][j];  /// <-is this not working? 

      Logger.log("Test Log:")
      Logger.log("This is the updated field stored in the wrapper:"+wrapper[fields[j]]) // Returns : "20220301"
      Logger.log("Lets check the wrapper if has the date/first value : " + wrapper.date ) // Returns "20220301"
      // the wrapper does not dissapear but appears as empty when accessed as in root, the assignment abovew worked and the key value pair is accessible
      Logger.log("Wrapper : " + JSON.stringify(wrapper)) // This returns always "Wrapper : []"  Stringify is solely used to see that atleast something is returned and the wrapper is accesible
      Logger.log("This is the current cell: "+fields[j]+" : "+tableData[i][j]) // This returns : "This is the current cell: date : 20220301" ...  This is the current cell: medium : (none) 
      // So in conclusion All values and Arrays are accessible

        // store the column data in the current row array, using the column header as the key
        


      }
      
      // add the current row to the new array of parsed data
      newtableData.push(wrapper);
    }
    
    
    // return the new array of parsed data
    Logger.log(newtableData)  //This returns: "[[], [], [], [], []]""
    return newtableData;
  
  // if there is an error parsing the data, print the error to the log
  } catch (e) {
    Logger.log("Error parsing data")
    Logger.log(e)
  }
}

#Edit: Added some logging and comments