Refresh External Data Variables with Conditions

I have getQueryStringParameters("") which is set to pull data from the URL into a Form Variable. That form variable is used as a condition to query an external data source and return one row.

During testing in the Preview tab of the Form Designer, it appears that the external data source does not update with the new query string parameter.

Not sure if this works once published but I hope it does. For now, I can confirm that it definitely does not work in the Form Designer - Preview tab. This is problematic, at the very least, in Preview testing and of course simply untestable in Workflow Testing (as it does not allow setting of query string parameters).