WooCommerce Rest-Api for getting variable product missing attributes

After each order I want to extract using rest api the orders info including all info about the order products.

I call the rest api for the order id and then the rest api for each productid or variation_id.

https://SHOPURL.com/wp-json/wc/v3/products/1234?consumer_key=YYYY&consumer_secret=YYYY

I get in result json with all the details about the product with id 1234, including all of it’s attributes.
Assuming there are attributes A and B, while for the product A defined with the optional value (a1), and B with two values (b1 and b2), I get the following in the Json – as expected:

"attributes": [
    {
        "id": 9,
        "name": "A",
        "slug": "A",
        "position": 0,
        "visible": true,
        "variation": false,
        "options": [
            "a1"
        ]
    },
    {
        "id": 10,
        "name": "B",
        "slug": "pa_hs_code",
        "position": 1,
        "visible": true,
        "variation": false,
        "options": [
            "B1",
            "B2",
        ]
    }
],

However, if the product ID is variation_id of a variable product with the same attribute A (a1) and B (b1,b2), while attribute B is defined to be the attribute for variation with 2 variation b1 and b2, I do NOT get attribute A in the Json, only the variation attribute with the selected value. Attribute A is not there!

    "attributes": [
        {
            "id": 15,
            "name": "B",
            "slug": "B",
            "option": "b1"
        }
    ],

I would expect to haver at the variation_id all attributes of the product including the variation attributes. Is it a bug or should I also call the rest api of the product_id (the father of the variation_id) to get the full list of attributes.

Please help.