Creating hosted zone records with .NET SDK

I am trying to create hosted zone records (alias, Simple routing, A records) using the .NET SDK ChangeResourceRecordSetsAsync method. My jsonized input for the request (sanitized) is this:

{
  "HostedZoneId": "route 53 hosted zone id",
  "ChangeBatch": {
    "Changes": [
      {
        "Action": {
          "Value": "CREATE"
        },
        "ResourceRecordSet": {
          "Name": "uri that i wish this to appear as",
          "Type": {
            "Value": "A"
          },
          "Region": {
            "Value": "selected region"
          },
          "AliasTarget": {
            "HostedZoneId": "hosted zone id of the api gateway endpoint",
            "DNSName": "api gateway domain name",
            "EvaluateTargetHealth": true
          },
        }
      }
    ]
  }
}

If I include SetIdentifier, I end up with a hosted zone record, but the routing is set to Latency. If I remove SetIdentifier, it complains because it is not there and nothing gets created. Could someone please help me format a request to create a record with Simple routing?