Position Validation while creating Job requisition

Summary:

We have a validation in the Responsive UI: while creating a Job Requisition, if the selected position is not vacant, it throws an error. We achieved this using ACR.

However, I am not able to achieve the same in Redwood.

Content (please ensure you mask any confidential information):

Oracle 25C ORC doc shows that a similar validation is possible. Has anyone tried to achieve it?

I created the following validation to check the difference between the position headcount/FTE and the active incumbent headcount/FTE, but it doesn’t seem to work.
From my observation, the values for these headcount/FTE variables are mostly coming back as null, because when I test the validation using an IF NULL statement, it works.