AWS SDK in javascript - BatchWriteItemCommand - String array imported as string set not a array of strings

I am inserting an dynamodb record which contains an array and it is coming up as a DynamoDB StringSet, rather than a List of strings. i am using

import {
  DynamoDBClient,
  BatchWriteItemCommand,
  ScanCommand,
} from "@aws-sdk/client-dynamodb";
import dbDataTypes from "dynamodb-data-types";

const REGION = "ap-southeast-2";
const dbclient = new DynamoDBClient({ region: REGION });
export function buildPutStatement(data) {
  let dynamoDBRecords = data.map((record) => {
    record = dbDataTypes.AttributeValue.wrap(record);
    let dynamoRecord = Object.assign({ PutRequest: { Item: record } });
    return dynamoRecord;
  });
  return dynamoDBRecords;
}

try {
  const tableName = "shipmentData";
  let records = [{
    modifiedAt: "2023-02-16T04:37:45.826Z",
    modifiedBy: "test script Feb 2023",
    shipmentId: "11122a56-0b8c-4a14-ba70-f5d7dfa6b22f",
    tag: "AportGuids",
    value: {
      timestamp: 1676522265826,
      guids: [
        "07088ea1-cb53-4bd3-b7a7-2a1fdf1e99ca",
        "30dce880-0b00-4682-b612-4b54dbf7caef",
      ],
    },
  }];

  const putStatements = buildPutStatement(records);

  let requestItems = {};
  requestItems[tableName] = putStatements;

  var params = {
    RequestItems: requestItems,
  };

  await dbclient.send(new BatchWriteItemCommand(params));

  console.log(records?.length + " Records processed");
} catch (err) {
  console.log("Error", err);
}

It is getting converted to dynamo Db Json format with an SS (String Set) as follows...

 "modifiedBy": {
    "S": "test script Feb 2023"
  },
  "value": {
    "M": {
      "guids": {
        "SS": [
          "07088ea1-cb53-4bd3-b7a7-2a1fdf1e99ca",
          "30dce880-0b00-4682-b612-4b54dbf7caef"
        ]
      },
      "timestamp": {
        "N": "1676522265826"
      }

rather than an L or S (Strings)...

"value": {
  "M": {
   "disportGuids": {
    "L": [
     {
      "S": "1dc8a478-d2af-4d84-ba57-4b1be4fb3c7c"
     },
     {
      "S": "dbe47150-1940-44cf-a264-421e63f0aacd"
     }
    ]
   },
   "timestamp": {
    "S": "1676273448403"
   }

This L of S (List of Strings) is what i get when i post through my web portal via AppSync. Note this is returned as a String[] in the json.

The main issue is when i retreive it in my lambda with the following...

const p = new Promise<any[]>((resolve, reject) => {
      this.ddb.query(
        {
          ExpressionAttributeValues: {
            ":v1": id,
          },
          KeyConditionExpression: "id = :v1",
          TableName: this.sourceTable,
        },
        (err: any, data: any) => {

i cannot iterate through it as it comes out in a different format again. e.g.

{ "values":{
    "type": "String",
     "values": ["1dc8a478-d2af-4d84-ba57-4b1be4fb3c7c", "dbe47150-1940-44cf-a264-421e63f0aacd"],
     "wrapperName": "Set"
}}

rather then just... ["1dc8a478-d2af-4d84-ba57-4b1be4fb3c7c", "dbe47150-1940-44cf-a264-421e63f0aacd"]

Notes/questions?

1. In the AWS console when I edit the record, the "View DynamoDB JSON" toggle is disabled. Why is this? I assume it thinks it is corrupted.
2. if I append a null to the array before posting it, it comes out in the desired format, but then I have a null in the array which I will have to code for.
3. How to i get it to store in the desired format e.g. a string[]?