Bulk activity extract with specific list of fields for creating job still generates output with the same default fields

[Saheli_Dey1]

Rest endpoint:bulk/v1/activities/export/create.json

JSON payload when creating job is:

But the output when downloading the results shows all default fields:

marketoGUID,leadId,activityDate,activityTypeId,campaignId,primaryAttributeValueId,primaryAttributeValue,attributes

{
   "format" : "CSV",
   "filter" : {
      "createdAt" : {
         "startAt" : "2020-10-27T23:59:59-00:00",
         "endAt" : "2020-10-28T23:59:59-00:00"
      },
      "activityTypeIds" : [ 12 ],
      "columnHeaderNames" : {
         "leadId" : "ID",
         "activityTypeId" : "activityTypeId"
      },
      "fields" : [ "leadId", "activityTypeId" ]
   }
}

I wanted to use the smaller subset of fields to reduce the amount of data being retrieved. The documentation I am using is https://developers.marketo.com/rest-api/bulk-extract/bulk-activity-extract/

I am able to restrict the fields to just leadId - when calling bulk api for leads.

Is this a bug ?

[SanfordWhiteman]

IIRC fields is a top-level property, not a property of filter.