Timesheets and pay
The timesheet is what happened, not what you hoped would happen.
A rostered shift is a plan. A timesheet is a fact. Keeping those two apart, and paying people from the second one, is the difference between a pay run you approve in an afternoon and a pay run you reconstruct.
The part that is hard to copy
One shift, four outputs, nobody retyping
The same shift becomes the timesheet, the billable, the claim line and the payslip. Nothing is re-keyed at any of those handovers, so the money you claim and the money you pay come from one fact — instead of from two systems that agree right up until the fortnight they do not.