This is a limitation of function "@DocDescendants" which has been mentioned in the below document.
"This @function is calculated when the document is opened. Results are undefined in cases where the document is not opened."
The tool calculated the formula through the Notes API, so it cannot get the formula value.
We have logged a request for a product enhancement. Product enhancement ID is TFS0000478.
Our product management team reviews enhancement requests considering them for inclusion in a future product release. We will keep your service request open until a decision has been made regarding your request. There is no guarantee that a specific enhancement request will be implemented in a future release and you will receive updates regarding the status of your request.
Please refer to the "New Features" section of the Product Release Notes for a complete list of Enhancement ID's addressed in the new release. These are available in our Documentation section of the Support Portal.
For more information regarding our enhancement request policy, refer to our Global Support Guide on the Support Portal at www.quest.com/support