Why can't I access ItemValue from a dropdown question which uses choicesFromQuestion prop to derive its items from another tagbox question?

[kalpadiptyaroy]

Consider the following JSON, to understand the issue:

Provided definition for custom function is:

function getItemValueProp([val, qName, propName]) {
    if (!val || !qName || !propName) return ""; 

    const dropdown = this.survey.getQuestionByName(qName);
    if (!dropdown || !dropdown.selectedItem) return ""; 

    return dropdown.selectedItem[propName] || "";
}

surveyjs json config

[
    {
        "type": "tagbox",
        "name": "q1",
        "choices": [
            {
                "text": "service1",
                "value": "service1",
                "action": "action1"
            },
            {
                "text": "service2",
                "value": "service2",
                "action": "action2"
            }
        ]
    },
    {
        "type": "dropdown",
        "name": "q2",
        "choicesFromQuestion": "q1",
        "choicesFromQuestionMode": "selected"
    },
    {
        "type": "expression",
        "name": "e1",
        "expression": "{q2}" // This doesn't work, q2 value doesn't appear.
    },
    {
        "type": "expression",
        "name": "e2",
        "expression": "getItemValueProp({q2}, 'q2', action)" // Here it logs null for val in the console and doesn't work.
    }
]

What is the correct way of fetching the action fields value for the selected choice item from the dropdown when dropdown items are derived from a tagbox?

Kindly guide the correct approach or a walkaround.

Thanks,
Kalpadiptya