Scenario:

Administrator wants his supervisors to know the users who are yet to submit the timesheet. The admin is able to run the time report with the approval status filter and column enabled but, he is not able to find the users for whom the timesheet is yet to generate.

Workaround:
Enable access to historical timesheet for the supervisors. However this would enable the supervisor to view everyone's timesheet.
Or
Run the report with the approval status filter & approval status column enabled and then export the data into a Excel sheet, compare the user names on the Excel sheet with the list of users who are supposed to submit the timesheet.