I have used it in the past, I don’t think you have to link it to the workflowusertask yourself. Are you sure that data is in the list that you return and that the user is authorised to see these users?
I have used below microflow to generate the list..
I have checked in the local postgress database that the users are added to the workflowusertask (table system$workflowusertask_targetusers)
What have you used to display the target users?