Why is the timesheet status closed when approval status is pending?
There are only two 'Timesheet Status' options which are open and closed. If a timesheet has been submitted and not approved yet, the 'Timesheet Status' will state 'Closed.'
However, if a timesheet hasn't been submitted then the 'Timesheet Status' will state 'Open.'
Below is a help article in regard to the Timesheets Data Model.