Why do some transactions have no transaction type?

[yzh-d]

As shown in the following transaction, tx_types is empty. Under what circumstances will tx_types be empty? In addition, what does the type field mean?

api：api/v2/transactions/0xf93235b504c35058f552a07bb39f8b8f40e1094a8cb96912906b91a3c43ae16b
response：

{
    "timestamp": "2023-09-27T08:33:37.000000Z",
    "fee": {
        "type": "actual",
        "value": "21600000000000000"
    },
    "gas_limit": "32400",
    "block": 935,
    "status": "ok",
    "method": null,
    "confirmations": 568,
    "type": 2,
    "exchange_rate": null,
    "to": {
        "hash": "0x0000000000000000000000000000000000001002",
        "implementation_name": null,
        "is_contract": false,
        "is_verified": false,
        "name": null,
        "private_tags": [],
        "public_tags": [],
        "watchlist_names": []
    },
    "tx_burnt_fee": "21600000000000000",
    "max_fee_per_gas": "1000000000000",
    "result": "success",
    "hash": "0xf93235b504c35058f552a07bb39f8b8f40e1094a8cb96912906b91a3c43ae16b",
    "gas_price": "1000000000000",
    "priority_fee": "0",
    "base_fee_per_gas": "1000000000000",
    "from": {
        "hash": "0x13f30647b99Edeb8CF3725eCd1Eaf545D9283335",
        "implementation_name": null,
        "is_contract": false,
        "is_verified": null,
        "name": null,
        "private_tags": [],
        "public_tags": [],
        "watchlist_names": []
    },
    "token_transfers": [],
    "tx_types": [],
    "gas_used": "21600",
    "created_contract": {
        "hash": "0x0000000000000000000000000000000000000000",
        "implementation_name": null,
        "is_contract": true,
        "is_verified": null,
        "name": null,
        "private_tags": [],
        "public_tags": [],
        "watchlist_names": []
    },
    "position": 0,
    "nonce": 82,
    "has_error_in_internal_txs": null,
    "actions": [],
    "decoded_input": null,
    "token_transfers_overflow": false,
    "raw_input": "0xe6bfc3cf0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000000",
    "value": "0",
    "max_priority_fee_per_gas": "1000000000000",
    "revert_reason": null,
    "confirmation_duration": [
        0,
        2582192.0
    ],
    "tx_tag": null
}